#include<stdio.h>

int main(void){
    int K, A, B,a,b;
    scanf("%d",&K);
    scanf("%d %d",&A, &B);
    a = A/K;
    b = B/K;
    if(b > a){
        printf("OK\n");
    }
    else{
        if(A%K == 0){
            printf("OK\n");
        }
        else{
            printf("NG\n");
        }
    }
    return 0;
}