#include<stdio.h>

int main(){
	int kelipatan,batas1,batas2;
	scanf("%d %d %d", &kelipatan,&batas1,&batas2);
	int temp=batas2/kelipatan;
	if(temp*kelipatan>=batas1){
		printf("OK\n");
	}
	else printf("NG\n");
	return 0;
}