#include <bits/stdc++.h>
using namespace std;
long long sum(long long x, long long y) { return x + y; }
int main() {
  int n;
  cin >> n;
  long long mx = -11111;
  while (n--) {
    long long t, z;
    cin >> t >> z;
    mx = max(mx, sum(t, z));
  }
  cout << mx << endl;
  return 0;
}
