# ABC165A - We Love Golf

def main():
    # input
    K = int(input())
    A, B = map(int, input().split())

    # compute
    flag = False
    for i in range(A, B+1):
        if i%K == 0:
            flag = True

    # output
    if flag:
        print('OK')
    else:
        print('NG')


if __name__ == '__main__':
    main()

# ABC165A - We Love Golf

def main():
    # input
    K = int(input())
    A, B = map(int, input().split())

    # compute
    flag = False
    for i in range(A, B+1):
        if i%K == 0:
            flag = True

    # output
    if flag:
        print('OK')
    else:
        print('NG')


if __name__ == '__main__':
    main()

# ABC165A - We Love Golf # input # compute # output