#include <stdio.h>


int main()
{
  int k, a, b;
  int amod;
  
  scanf("%d",&k);
  scanf("%d %d", &a, &b);
  
  amod = a%k;
  a = a/k;
  b = b/k;

  if (amod == 0 || b > a) {
    printf("OK\n");
  } else {
    printf("NG\n");
  }

  return 0;
}