#include <bits/stdc++.h>
using namespace std;
signed main() {
  long long n;
  cin >> n;
  long long ans = 0;
  for (long long i = 0; i < n; ++i) {
    long long a, b;
    cin >> a >> b;
    ans = max(ans, a + b);
  }
  cout << ans;
}
