#include<stdio.h>
#define N 5

int main(void){
	int t,r0,r1,F = 1;
  	scanf("%d",&t);
  	scanf("%d",&r0);
  	scanf("%d",&r1);
  
  	
  	r0 = r0 / t;
	if(r0 != r1)
      	r0++;
  	//printf("r0 = %d\n",r0);
  
  	for(;r0 <= r1 / t;r0++){
      //printf("%d",r0 * t);
    	F = 0;
      	break;
    }
  	if(F)
      printf("NG\n");
  	else
      printf("OK\n");
  
 	 return 0;
}