#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, a, b;
  vector<int> v;
  cin >> n;
  for (int i = 0; i < n; ++i) {
    cin >> a >> b;
    v.push_back(a + b);
  }
  sort(v.begin(), v.end());
  while (1) {
    int cnt = 1;
    bool check = true;
    vector<int> t;
    for (int i = 0; i < v.size(); ++i) {
      if (i != v.size() - 1 && v[i] == v[i + 1]) {
        cnt++;
      } else {
        if (cnt >= 2) check = false;
        for (int j = 0; j < cnt / 2; ++j) {
          t.push_back(v[i] + 1);
        }
        if (cnt % 2 == 1) t.push_back(v[i]);
        cnt = 1;
      }
    }
    if (check) break;
    v = t;
  }
  for (auto elem : v) {
    cout << elem << " " << 0 << endl;
  }
  return 0;
}
