#include<stdio.h>
int main()
{
	int k,a,b;
	int i,j;
	scanf("%d %d %d",&k,&a,&b);
	i=1;
	while(1){
		i=k*j;
		j++;
		if(i>=a&&i<=b){
			printf("OK\n");
			break;
		}
		else if(i>=b){	
			printf("NG\n");
			break;
		}
	}
	return 0;
}
