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