#include <bits/stdc++.h>
using namespace std;
int n, res;
int main() {
  ios_base ::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  cin >> n;
  for (int i = 1; i <= n; i++) {
    int first, second;
    cin >> first >> second;
    res = max(res, first + second);
  }
  cout << res;
}
