#include <bits/stdc++.h>
using namespace std;
int main() {
  long int n, x, y, max = 0, temp = 0;
  cin >> n;
  for (long int i = 0; i < n; i++) {
    cin >> x >> y;
    temp = x + y;
    if (max < temp) {
      max = temp;
    }
  }
  cout << max;
  return 0;
}
