#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int x, y;
  long double maxd = 0.00000000;
  long long int ans = 0;
  long long int n;
  cin >> n;
  while (n--) {
    long long int a, b;
    cin >> a >> b;
    ans = max(ans, (a + b));
  }
  cout << ans << endl;
}
