#include <bits/stdc++.h>
#pragma warning(disable : 4996)
using namespace std;
using ld = long double;
const ld eps = 1e-9;
int main() {
  int N;
  cin >> N;
  vector<int> v(3e5);
  for (int i = 0; i < N; ++i) {
    int a, b;
    cin >> a >> b;
    v[a + b]++;
  }
  for (int i = 0; i < 2e5 + 10; ++i) {
    v[i + 1] += v[i] / 2;
    v[i] %= 2;
  }
  for (int i = 0; i < 2e5 + 10; ++i) {
    if (v[i]) {
      cout << i << " " << 0 << endl;
    }
  }
  return 0;
}
