#include <bits/stdc++.h>
const double E = 1e-8;
const double PI = acos(-1);
using namespace std;
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int t;
  cin >> t;
  pair<long long, long long> pto;
  int ans = 0;
  while (t--) {
    int x, y;
    cin >> x >> y;
    ans = max(ans, x + y);
  }
  cout << ans << '\n';
  return 0;
}
