def resolve():

    K = int(eval(input()))

    A, B= list(map(int, input().split())) 



    for i in range(A, B+1):

        if i % K == 0:

            print("OK")

            return



    print("NG")

    return





if __name__ == "__main__":

    resolve()
import math



def resolve():

    K = int(eval(input()))

    A, B= list(map(int, input().split())) 



    if A <= math.floor(B/K) * K:

        print("OK")

    else:

        print("NG")





if __name__ == "__main__":

    resolve()
def resolve():
    K = int(eval(input()))
    A, B = list(map(int, input().split()))
    for i in range(A, B + 1):
        if i % K == 0:
            print("OK")
            return
    print("NG")
    return


if __name__ == "__main__":
    resolve()

import math


def resolve():
    K = int(eval(input()))
    A, B = list(map(int, input().split()))
    if A <= math.floor(B / K) * K:
        print("OK")
    else:
        print("NG")


if __name__ == "__main__":
    resolve()

+import math + + -    for i in range(A, B + 1): -        if i % K == 0: -            print("OK") -            return -    print("NG") -    return +    if A <= math.floor(B / K) * K: +        print("OK") +    else: +        print("NG")