#include <bits/stdc++.h>
using namespace std;
int m[200000 + 1];
int main() {
  int n;
  scanf("%d", &n);
  while (n--) {
    int a, b;
    scanf(" %d %d", &a, &b);
    m[a + b]++;
  }
  for (int i = 0; i < 200000; i++) {
    m[i + 1] += m[i] / 2;
    m[i] = m[i] % 2;
    if (m[i] > 0) {
      cout << i << " " << 0 << endl;
    }
  }
  return 0;
}
