199.cpp

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#define INF 0x7FFFFFFF
using namespace std;
struct node{
    int s,b,num;
}per[200100];
node perr[200100];
int f[200100],g[200100],gg[200100],mark[200100],pre[1001000];
int n,pos;
int cmp(const void *a,const void *b){
    struct node * aa = (node *)a;
    struct node * bb = (node *)b;
    if (aa->s!=bb->s)
	return aa->s>bb->s;
    else 
	return aa->b<bb->b;
}
void dfs(int p){
    if (pre[p]>0)
	dfs(pre[p]);
    cout << perr[p].s << " " << perr[p].b << endl;
}
int main(){
    //freopen("199.in","r",stdin);
    //freopen("199.out","w",stdout);
    //init
    std::ios::sync_with_stdio(false);
    cin >> n;
    for (int i=1;i<=n;++i){
	cin >> per[i].s >> per[i].b;
	per[i].num = i;
	perr[i]=per[i];
    }
    qsort(per+1,n,sizeof(per[1]),cmp);
    //solve
    memset(mark,-1,sizeof(mark));
    fill(g+1,g+n+1000,INF);gg[0]=-1;
    fill(gg+1,gg+n+1000,INF);g[0]=-1;
    //fill(gg+1,gg+n+1000,INF);
    for (int i=1;i<=n;++i){
	
    }
    //print
    pos = *max_element(f+1,f+n+1);
    cout << pos << endl;
    pos = mark[pos];
    dfs(pos);
    putchar(10);
    return 0;
}