mod = 1000000007
eps = 10**-9


def main():
    import sys
    input = sys.stdin.readline

    A = input().rstrip('\n')
    B = input().rstrip('\n')

    L = set()
    for i in range(12346):
        L.add(str(i))

    if A in L and B in L:
        print("OK")
    else:
        print("NG")


if __name__ == '__main__':
    main()