#include <bits/stdc++.h>
using namespace std;
int main() {
  int long long t, n, cnt = 0, as, k, maxi = 0, mi, x, y;
  cin >> n;
  int long long arr[n];
  for (int i = 0; i < n; i++) {
    cin >> x >> y;
    maxi = max(maxi, x + y);
  }
  cout << maxi << endl;
}
