#include<stdio.h>
int main()
{
  int n,a,b;
  scanf("%d\n %d %d",&n,&a,&b);
  int l=0;
  for(int i=a;i<=b;i++)
  {
    if(i%n==0)
    {
      printf("OK\n");
      l++;
      break;
    }
  }
  if(l==0)
  {
  printf("NG\n");}
  
}