def main():
    A = input()
    B = input()

    ans = 'NG'
    if A.isdecimal() and B.isdecimal():
        if len(A) == 1 or A[0] != '0':
            if len(B) == 1 or B[0] != '0':
                ans = 'OK'

    print(ans)

main()