diff --git a/Lesson-1/assignment/yours.sol b/Lesson-1/assignment/yours.sol
index dfdb2c48..ea1b9978 100644
--- a/Lesson-1/assignment/yours.sol
+++ b/Lesson-1/assignment/yours.sol
@@ -1 +1,61 @@
 /*作业请提交在这个目录下*/
+pragma solidity ^0.4.14;
+
+contract Payroll {
+    uint constant payDuration = 10 seconds;
+
+    address owner;
+    uint salary;
+    address employee;
+    uint lastPayday;
+
+    function Payroll() {
+        owner = msg.sender;
+    }
+    
+    //修改员工地址 
+    function changeEmployee(address e) {
+        //只有合约部署者才有权限改变员工地址
+        require(msg.sender == owner);
+        
+        if (employee != 0x0) {  //员工地址地址不能是0 
+            //发放未领取的工资  
+            uint payment = salary * (now - lastPayday) / payDuration;
+            employee.transfer(payment);
+        }
+        employee = e;
+        lastPayday = now;
+    }
+    
+    //更改跟员工薪水
+    function changeSalary(uint money){ 
+      //只有合约部署者才有权限改变员工薪水。money 默认参数是wei，需要转化。         
+      require(msg.sender==owner);
+       
+      salary = money * 1 ether;
+      
+    }
+
+    
+    function addFund() payable returns (uint) {
+        return this.balance;
+    }
+    
+    function calculateRunway() returns (uint) {
+        return this.balance / salary;
+    }
+    
+    function hasEnoughFund() returns (bool) {
+        return calculateRunway() > 0;
+    }
+    
+    function getPaid() {
+        require(msg.sender == employee);
+        
+        uint nextPayday = lastPayday + payDuration;
+        assert(nextPayday < now);
+
+        lastPayday = nextPayday;
+        employee.transfer(salary);
+    }
+}
diff --git a/Lesson-3/assignment/Ownable.sol b/Lesson-3/assignment/Ownable.sol
new file mode 100644
index 00000000..a1efe5bb
--- /dev/null
+++ b/Lesson-3/assignment/Ownable.sol
@@ -0,0 +1,42 @@
+pragma solidity ^0.4.18;
+
+
+/**
+ * @title Ownable
+ * @dev The Ownable contract has an owner address, and provides basic authorization control
+ * functions, this simplifies the implementation of "user permissions".
+ */
+contract Ownable {
+  address public owner;
+
+
+  event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);
+
+
+  /**
+   * @dev The Ownable constructor sets the original `owner` of the contract to the sender
+   * account.
+   */
+  function Ownable() public {
+    owner = msg.sender;
+  }
+
+  /**
+   * @dev Throws if called by any account other than the owner.
+   */
+  modifier onlyOwner() {
+    require(msg.sender == owner);
+    _;
+  }
+
+  /**
+   * @dev Allows the current owner to transfer control of the contract to a newOwner.
+   * @param newOwner The address to transfer ownership to.
+   */
+  function transferOwnership(address newOwner) public onlyOwner {
+    require(newOwner != address(0));
+    OwnershipTransferred(owner, newOwner);
+    owner = newOwner;
+  }
+
+} 
diff --git a/Lesson-3/assignment/SafeMath.sol b/Lesson-3/assignment/SafeMath.sol
new file mode 100644
index 00000000..d27c3cc5
--- /dev/null
+++ b/Lesson-3/assignment/SafeMath.sol
@@ -0,0 +1,47 @@
+pragma solidity ^0.4.18;
+
+/**
+ * @title SafeMath
+ * @dev Math operations with safety checks that throw on error
+ */
+library SafeMath {
+
+  /**
+  * @dev Multiplies two numbers, throws on overflow.
+  */
+  function mul(uint256 a, uint256 b) internal pure returns (uint256) {
+    if (a == 0) {
+      return 0;
+    }
+    uint256 c = a * b;
+    assert(c / a == b);
+    return c;
+  }
+
+  /**
+  * @dev Integer division of two numbers, truncating the quotient.
+  */
+  function div(uint256 a, uint256 b) internal pure returns (uint256) {
+    // assert(b > 0); // Solidity automatically throws when dividing by 0
+    uint256 c = a / b;
+    // assert(a == b * c + a % b); // There is no case in which this doesn't hold
+    return c;
+  }
+
+  /**
+  * @dev Subtracts two numbers, throws on overflow (i.e. if subtrahend is greater than minuend).
+  */
+  function sub(uint256 a, uint256 b) internal pure returns (uint256) {
+    assert(b <= a);
+    return a - b;
+  }
+
+  /**
+  * @dev Adds two numbers, throws on overflow.
+  */
+  function add(uint256 a, uint256 b) internal pure returns (uint256) {
+    uint256 c = a + b;
+    assert(c >= a);
+    return c;
+  }
+} 
diff --git a/Lesson-3/assignment/addEmployee.jpeg b/Lesson-3/assignment/addEmployee.jpeg
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diff --git a/Lesson-3/assignment/caculateRunaway.jpeg b/Lesson-3/assignment/caculateRunaway.jpeg
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diff --git a/Lesson-3/assignment/checkEmployee.jpeg b/Lesson-3/assignment/checkEmployee.jpeg
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diff --git a/Lesson-3/assignment/removeEmployee.jpeg b/Lesson-3/assignment/removeEmployee.jpeg
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diff --git a/Lesson-3/assignment/transferOwnership.jpeg b/Lesson-3/assignment/transferOwnership.jpeg
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diff --git a/Lesson-3/assignment/yours.sol b/Lesson-3/assignment/yours.sol
index dfdb2c48..e72ece24 100644
--- a/Lesson-3/assignment/yours.sol
+++ b/Lesson-3/assignment/yours.sol
@@ -1 +1,186 @@
 /*作业请提交在这个目录下*/
+
+pragma solidity ^0.4.21;
+
+import "./Ownable.sol";
+import "./SafeMath.sol";
+
+contract Payroll is Ownable  {
+
+    using SafeMath for  uint;
+
+    struct Employee {
+        address id ;
+        uint salary ;
+        uint lastPayDay ;
+    }
+
+    //Employee [] employees;
+
+    mapping(address => Employee ) public  employees;
+
+    uint salary = 0 ether;
+
+    //雇主 地址
+    address owner = 0x0 ;
+    //员工地址
+   // address employeeAddress = 0x0 ;
+    // 支付周期
+    uint constant payDuration = 10 seconds ;
+   //上次支付时间
+    uint lastPayDay = now;
+
+    uint totalSalary;
+
+    // modifier onlyOwner {
+    //     require(msg.sender == owner);
+    //     _;
+    // }
+
+    modifier employeeExist(address employeeId) {
+        var employee = employees[employeeId];
+        assert(employee.id != 0x0);
+        _;
+    }
+
+
+    modifier employeeNotExist(address employeeId) {
+        var employee = employees[employeeId];
+        assert(employee.id == 0x0);
+        _;
+    }
+
+
+
+    // init method
+    // function Payroll(){
+    //     owner = msg.sender;
+    // }
+
+    // 支付 部分工资
+    function _partialPay(Employee employee) private {
+        //assert(employee.id != 0x0);
+        uint payment = employee.salary.mul( now.sub( employee.lastPayDay ) ).div(payDuration) ;
+        employee.id.transfer(payment);
+
+    }
+
+    /*
+    function _findEmployee(address employeeId) private returns (Employee ,uint) {
+          for ( uint i= 0; i< employees.length ; i++ ){
+            if ( employees[i].id == employeeId ) {
+                return ( employees[i] ,i);
+            }
+        }
+    }*/
+
+    function addEmployee( address employeeId, uint salary  ) onlyOwner  employeeNotExist(employeeId){
+        // require(msg.sender == owner);
+        //Employee e =_findEmployee(employeeId);
+       // var (employee , index ) = employees[employeeId];
+       var employee = employees[employeeId];
+        //_findEmployee(employeeId);
+        // 异常
+        // assert(employee.id == 0x0);
+        //employees.push(Employee(employeeId,salary * 1 ether,now));
+        // totalSalary +=salary * 1 ether ;
+
+        totalSalary = totalSalary.add(salary.mul(1 ether ));
+
+        employees[employeeId]=Employee(employeeId,salary .mul(1 ether),now);
+    }
+
+    function removeEmployee(address employeeId) onlyOwner  employeeExist(employeeId) {
+        // require(msg.sender == owner);
+
+       // var (employee , index ) = _findEmployee(employeeId);
+        var employee = employees[employeeId];
+        // assert(employee.id != 0x0);
+        _partialPay(employee);
+
+
+        // totalSalary += employee.salary * 1 ether ;
+        totalSalary = totalSalary.sub(salary.mul(1 ether));
+        delete  employees[employeeId];
+
+        // employees[index] = employees[employees.length - 1];
+        // employees.length -= 1;
+
+
+    }
+
+    function updateEmployee(address employeeId,uint  salary )  onlyOwner  employeeExist(employeeId) {
+        // require(msg.sender == owner);
+
+        // var (employee , index ) = _findEmployee(employeeId);
+        var employee = employees[employeeId];
+
+        totalSalary = totalSalary.sub(employee.salary).add(salary.mul(1 ether));
+
+        employees[employeeId].id = employeeId;
+        employees[employeeId].salary = salary.mul(1 ether);
+        employees[employeeId].lastPayDay = now;
+
+
+    }
+
+    function addFund()  payable returns (uint) {
+      // add money to contract
+      return this.balance ;
+    }
+
+    function  getFund () returns (uint) {
+        return this.balance ;
+    }
+
+    function caculateRunaway() returns (uint){
+        // uint totalSalary = 0;
+
+
+        // for ( uint i= 0; i< employees.length ; i++){
+        //     totalSalary += employees[i].salary ;
+
+        // }
+
+        assert(totalSalary !=0 );
+        assert( this.balance !=0 );
+        return this.balance.div(totalSalary) ;
+    }
+
+
+
+    function hasEnoughFund() returns (bool) {
+        // return this.balance >= salary ;
+        // this 方法 gas 高
+       return  caculateRunaway()>0 ;
+    }
+
+    function checkEmployee (address employeeId ) returns (uint salary ,uint lastPayDay ) {
+        var employee = employees[employeeId];
+        // return (employee.salary ,employee.lastPayDay );
+        salary = employee.salary ;
+        lastPayDay = employee.lastPayDay;
+    }
+
+    function getPaid()   employeeExist(msg.sender)  {
+        var employee = employees[msg.sender];
+        //var ( employee ,index) = _findEmployee(msg.sender);
+
+        //assert( employee.id != 0x0 );
+
+        uint nexPayDay = lastPayDay.add( payDuration);
+        // 确保 支付时间 正确
+        assert(nexPayDay < now);
+        /**
+         * if (nexPayDay > now ) {
+            revert() ;
+             exception no gas
+        }
+        */
+
+        lastPayDay = nexPayDay ;
+        // 发钱
+        employee.id.transfer(employee.salary);
+
+    }
+}