#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  pair<int, int> a[100000];
  cin >> n;
  for (int i = 0; i < n; i++) cin >> a[i].first >> a[i].second;
  int res = 0;
  for (int i = 0; i < n; i++) res = max(res, a[i].first + a[i].second);
  cout << res;
  return 0;
}
