#include <bits/stdc++.h>
using namespace std;
int main() {
  long long n, x, y;
  long long max1 = INT8_MIN;
  cin >> n;
  for (auto i = 0; i < n; i++) {
    cin >> x >> y;
    max1 = max(max1, x + y);
  }
  cout << max1 << endl;
  return 0;
}
