import sys



sys.setrecursionlimit(10 ** 7)

rl = sys.stdin.readline





def solve():

    K = int(rl())

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

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

        if i % K == 0:

            print("OK")

            exit()

    print("NG")





if __name__ == '__main__':

    solve()

def solve():

    K = int(eval(input()))

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

    k = B // K

    if k * K >= A:

        print("OK")

    else:

        print("NG")

    



if __name__ == '__main__':

    solve()

import sys

sys.setrecursionlimit(10**7)
rl = sys.stdin.readline


def solve():
    K = int(rl())
    A, B = list(map(int, rl().split()))
    for i in range(A, B + 1):
        if i % K == 0:
            print("OK")
            exit()
    print("NG")


if __name__ == "__main__":
    solve()

def solve():
    K = int(eval(input()))
    A, B = list(map(int, input().split()))
    k = B // K
    if k * K >= A:
        print("OK")
    else:
        print("NG")


if __name__ == "__main__":
    solve()

-import sys - -sys.setrecursionlimit(10**7) -rl = sys.stdin.readline - - -    K = int(rl()) -    A, B = list(map(int, rl().split())) -    for i in range(A, B + 1): -        if i % K == 0: -            print("OK") -            exit() -    print("NG") +    K = int(eval(input())) +    A, B = list(map(int, input().split())) +    k = B // K +    if k * K >= A: +        print("OK") +    else: +        print("NG")