#include <bits/stdc++.h>
using namespace std;
long long int a[100003], b[100003];
int main() {
  int n;
  cin >> n;
  long long int ans = 0;
  for (long i = 0; i < n; i++) {
    cin >> a[i] >> b[i];
    ans = max(ans, a[i] + b[i]);
  }
  cout << ans;
  return 0;
}
