#include <bits/stdc++.h>
using ll = long long;
using namespace std;
int main() {
  int t;
  cin >> t;
  int m = 0;
  while (t--) {
    int x, y;
    cin >> x >> y;
    if (m < x + y) {
      m = x + y;
    }
  }
  cout << m << endl;
  return 0;
}
