#include<stdio.h>
int main(void){
    int A,B,K,x;
    scanf("%d%d%d",&K,&A,&B);
        for(int i=A;i<=B;i++){
            if(i%K == 0){
                printf("OK\n");
                break;
            }else if(i==B) printf("NG\n");
        }
    return 0;
}