#include <bits/stdc++.h>
using namespace std;
int main() {
  long long n;
  cin >> n;
  long long x, y, dist, maxdist = 0;
  for (long long i = 0; i < n; i++) {
    cin >> x >> y;
    dist = x + y;
    if (maxdist < dist) {
      maxdist = dist;
    }
  }
  cout << maxdist;
}
