#include <stdio.h>

int hikyori(int dist)
{
  int A,B;
  int i;
  scanf("%d %d",&A,&B);

  if(1 <= K && K<= 1000)
  {
    if( 1 <= A && A <= B && B<= 1000)
    {
      for(i = A; i<=B;i++)
      {
        if( i % dist == 0)
        {
          printf("OK\n");
          flg = 1;
          return 0;
        }
      }
    }
  }
  printf("NG\n");
  return 0;
}

int main(void)
{
  int K;
  
  scanf("%d",&K);
  hikyori(K);
  return 0;
}