#include <bits/stdc++.h>
int main() {
  int n;
  scanf("%d", &n);
  long long int max = 0;
  for (int i = 0; i < n; i++) {
    long long int x, y, temp = 0;
    scanf("%lld %lld", &x, &y);
    temp = x + y;
    if (temp > max) {
      max = temp;
    }
  }
  printf("%lld", max);
}
