#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, a, b, i;
  vector<int> amo;
  cin >> n;
  for (i = 0; i < n; i++) {
    cin >> a >> b;
    a += b;
    amo.push_back(a);
  }
  int test, from;
  while (1) {
    test = 0;
    from = 0;
    sort(amo.begin(), amo.end());
    for (i = 0; amo[i] == -1; i++) from++;
    for (i = from; i < amo.size(); i++) {
      if (amo[i] == amo[i + 1]) {
        amo[i] = -1;
        amo[i + 1]++;
        test++;
      }
    }
    if (test == 0) break;
  }
  for (i = from; i < amo.size(); i++) cout << amo[i] << " 0" << endl;
  return 0;
}
