#include <bits/stdc++.h>
using namespace std;
signed main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  long long n, x, y, ans = 0;
  cin >> n;
  for (long long i = 0; i < n; i++) {
    cin >> x >> y;
    ans = max(ans, x + y);
  }
  cout << ans << "\n";
  return 0;
}
