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