#include <iostream>
#include <map>
using namespace std;
int main()
{
int N = 0;
cin >> N;
map<int,int> myMap;
myMap.clear();
for(int i = 0;i < N; i++){
pair<int,int> myPair;
cin >> myPair.first;
cin >> myPair.second;
if(myMap.find(myPair.first) != myMap.end()){
myMap[myPair.first] += myPair.second;
}else{
myMap[myPair.first] = myPair.second;
}
}
for(map<int,int>::iterator it = myMap.begin(); it != myMap.end();it++){
cout << it->first << ' ' << it->second << endl;
}
return 0;
}