#include <bits/stdc++.h>
using namespace std;
int32_t main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  long long n;
  cin >> n;
  long long maxi = INT_MIN;
  while (n--) {
    long long x, y;
    cin >> x >> y;
    long long sum = x + y;
    if (sum > maxi) {
      maxi = sum;
    }
  }
  cout << maxi << "\n";
  return 0;
}
