set的使用

#include<bits/stdc++.h>
using namespace std;


int main()
{
    int n;
    while( ~scanf("%d",&n) )
    {
        map<int,int> mp;
        while( n-- )
        {
            int key,value;
            scanf("%d%d",&key, &value );
            mp[key]+=value;
        }    

        for( auto it : mp )
        {
            printf("%d %d\n", it.first, it.second );
        }
    }

    return 0;
}