#include <bits/stdc++.h>
using namespace std;
int n;
int s[200005];
int main() {
  scanf("%d", &n);
  for (int i = 0; i < n; i++) {
    int x, y;
    scanf("%d %d", &x, &y);
    int z = x + y;
    while (s[z]) {
      s[z] = 0;
      z++;
    }
    s[z] = 1;
  }
  for (int z = 0; z < 200005; z++)
    if (s[z]) printf("%d 0\n", z);
  return 0;
}
