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

int main() {
    int n;
    int key, value;
    cin >> n;
    map<int, int> res;
    for (int i = 0; i < n; ++i) {
        cin >> key >> value;
        res[key] += value;
    }
    for (auto &[key, value] : res) {
        cout << key << " " << value << endl;
    }
}