#include<stdlib.h>
#include<stdio.h>
#include<string.h>



int main(){
    int A,B,K;
    scanf("%d %d %d",&K,&A,&B);
    for (int i=K; i<1000; i+=K) {
        if(A<=i && i<=B){
            printf("OK\n");
            return 0;
        }
    }
    printf("NG\n");
    return 0;
}