#include <stdio.h>

int main(void) {
    int k,a,b,large;

    scanf("%d",&k);
    scanf("%d %d",&a,&b);
    large = ((b / k) * k);
    if ( a <= large ){
        printf("OK\n");
    }else{
        printf("NG\n");
    }
	return 0;
}