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