#include <stdio.h>

int main(void){
    int K, A, B;
    int x;

    scanf("%d%d%d", &K, &A, &B);
    x = A + (K - A % K);
    if(A % K == 0 || x <= B)
        printf("OK\n");
    else
        printf("NG\n");

    return 0;
}
