#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <string.h>
int main(int argc, char *argv[]){
        long a,b,k;
        int i,f = 0;
        scanf("%ld\n", &k);
        scanf("%ld %ld", &a, &b);
        for(i = a; i <= b; i++){
                if(i % k == 0){
                        f = 1;
                }
        }
        if(f){
                printf("OK\n");
        }else{
                printf("NG\n");
        }
        return 0;
}