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