#include <iostream>
#include <map>

using namespace std;

/*
思路:采用map进行操作,若相同的key,则进行累加;若不存在,则添加
*/
int main()
{
    int N, key, value;
    map<int, int> mapIn;
    while(cin>>N) {
        for(int i = 0; i <  N; i++) {
            cin>>key>>value;
            if(mapIn.count(key) == 0) {
                mapIn.emplace(key, value);
            } else {
                mapIn[key] += value;
            }
        }
        
        for(auto iter = mapIn.begin(); iter != mapIn.end(); iter++) {
            cout<<iter->first<<" "<<iter->second<<endl;
        }
    }
    return 0;
}