#include <bits/stdc++.h>
int main() {
  int n;
  scanf("%d", &n);
  int maxx = -1, maxy = -1, max = -1;
  int i, x, y;
  for (i = 0; i < n; i++) {
    scanf("%d %d", &x, &y);
    if (x + y >= max) {
      max = x + y;
    }
  }
  printf("%d\n", max);
  return 0;
}
