#include <stdio.h>

int main(void)
{
  int k, a, b;

  scanf("%d%d%d", &k, &a, &b);
  /*
  (a/k != b/k) ? printf("Yes\n");
  : (a%k==0 || b%k ==0) ? printf("Yes\n");
      : printf("No\n");
  */


  if (a/k != b/k)
    printf("OK\n");
  else if (a%k == 0 || b%k == 0)
    printf("OK\n");
  else 
    printf("NG\n");

  return 0;
}
