#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;
}