#include<bits/stdc++.h>

using namespace std;

int main()
{
    map<int,int> data;

    int num;
    int m(0),n(0);
    while(cin>>num){
        while(num--){
            cin>>m>>n;
            data[m]+=n;
        }
        for(auto val: data){
            cout<<val.first<<' '<<val.second<<endl;
        }
    }
    return 0;
}

map的key默认对应的value是0.