#include <iostream>
#include <map>
using namespace std;

int main() {
    int n;
    cin >> n;
    map<int, int> m;
    int a, b;
    while(cin >> a >> b) {
        m[a] += b;
    }
    for(auto it: m) {
        cout << it.first << " " << it.second << endl;
    }
    return 0;
}