#include <bits/stdc++.h>
using namespace std;
int n, x, y, maxl = 1;
int main() {
  cin >> n;
  for (int i = 0; i < n; i++) {
    cin >> x >> y;
    maxl = max(maxl, x + y);
  }
  cout << maxl;
  return 0;
}
