diff --git a/.DS_Store b/.DS_Store
new file mode 100644
index 0000000..dc9ce7e
Binary files /dev/null and b/.DS_Store differ
diff --git a/40130212009/.DS_Store b/40130212009/.DS_Store
new file mode 100644
index 0000000..5008ddf
Binary files /dev/null and b/40130212009/.DS_Store differ
diff --git a/Answers/How To.txt b/40130212009/How To.txt
similarity index 100%
rename from Answers/How To.txt
rename to 40130212009/How To.txt
diff --git a/40130212009/findMissingNumber.js b/40130212009/findMissingNumber.js
new file mode 100644
index 0000000..f9b5847
--- /dev/null
+++ b/40130212009/findMissingNumber.js
@@ -0,0 +1,13 @@
+function findMissingNumber(array) {
+  let n = array.length;
+  let sum = (n * (n + 1)) / 2;
+  let sumOfElementArray = 0;
+  for (let i = 0; i < array.length; i++) {
+    sumOfElementArray += array[i];
+  }
+  let missingNumber = sum - sumOfElementArray;
+  return missingNumber;
+}
+
+let array = [0, 1, 2, 3, 5];
+console.log(findMissingNumber(array));
diff --git a/40130212009/maximumSubarraySum.js b/40130212009/maximumSubarraySum.js
new file mode 100644
index 0000000..9f09592
--- /dev/null
+++ b/40130212009/maximumSubarraySum.js
@@ -0,0 +1,22 @@
+function maximumSubarraySum(array) {
+  let n = array.length;
+  let max = array[0];
+  for (let i = 0; i < n; i++) {
+    let s = array[i];
+    if (s >= max) {
+      max = s;
+    }
+    let j = i + 1;
+    while (j < n) {
+      s += array[j];
+      if (s >= max) {
+        max = s;
+      }
+      j++;
+    }
+  }
+  return max;
+}
+
+let array = [1, 5, -1, -50, 3, 4, 7, -5];
+console.log(maximumSubarraySum(array));
diff --git a/40130212009/mergeSortedArrays.js b/40130212009/mergeSortedArrays.js
new file mode 100644
index 0000000..46498b8
--- /dev/null
+++ b/40130212009/mergeSortedArrays.js
@@ -0,0 +1,31 @@
+function mergeSortedArrays(array1, array2) {
+  let counter1 = array1.length - 1;
+  let counter2 = array2.length - 1;
+  let counterMerge = array1.length + array2.length - 1;
+
+  array1.length = counterMerge + 1;
+
+  while (counter1 >= 0 && counter2 >= 0) {
+    if (array1[counter1] > array2[counter2]) {
+      array1[counterMerge] = array1[counter1];
+      counter1--;
+    } else {
+      array1[counterMerge] = array2[counter2];
+      counter2--;
+    }
+    counterMerge--;
+  }
+
+  while (counter2 >= 0) {
+    array1[counterMerge] = array2[counter2];
+    counter2--;
+    counterMerge--;
+  }
+
+  return array1;
+}
+
+let array1 = [3, 6, 8, 11];
+let array2 = [1, 4, 5, 7, 9, 10];
+mergeSortedArrays(array1, array2);
+console.log(array1);
diff --git a/40130212009/removeDuplicates.js b/40130212009/removeDuplicates.js
new file mode 100644
index 0000000..bd611a4
--- /dev/null
+++ b/40130212009/removeDuplicates.js
@@ -0,0 +1,12 @@
+function removeDuplicates(array) {
+  let lenOfArray = 0;
+  for (let i = 0; i < array.length; i++) {
+    if (array[i] !== array[i - 1]) {
+      lenOfArray++;
+    }
+  }
+  return lenOfArray;
+}
+
+let array = [1, 2, 2, 3, 3, 3, 4, 5];
+console.log(removeDuplicates(array));
diff --git a/40130212009/rotateArray.js b/40130212009/rotateArray.js
new file mode 100644
index 0000000..2827ba3
--- /dev/null
+++ b/40130212009/rotateArray.js
@@ -0,0 +1,18 @@
+function rotateArray(arr, k) {
+  let n = arr.length;
+  k = k % n;
+  let rotatedArr = new Array(n);
+  for (let i = 0; i < k; i++) {
+    rotatedArr[i] = arr[n - k + i];
+  }
+
+  for (let i = k; i < n; i++) {
+    rotatedArr[i] = arr[i - k];
+  }
+
+  return rotatedArr;
+}
+
+let array = [1, 2, 3, 4, 5];
+let k = 2;
+console.log(rotateArray(array, k));