#include <bits/stdc++.h>
int main() {
  int n;
  scanf("%d", &n);
  int a, b, max1 = 0, max2 = 0;
  for (int i = 0; i < n; i++) {
    scanf("%d %d", &a, &b);
    if (a + b > max1) max1 = a + b;
  }
  printf("%d\n", max1);
  return 0;
}
