A = input()
B = input()

if len(A) >= 2:
    if A[0] == "0" and A[1] == "0":
        print("NG")
        exit()

if len(B) >= 2:
    if B[0] == "0" and B[1] == "0":
        print("NG")
        exit()


s = ["0", "1", "2", "3", "4", "5", "6", "7", "8", "9"]
for i in range(len(A)):
    if A[i] not in s:
        print("NG")
        exit()

for i in range(len(B)):
    if B[i] not in s:
        print("NG")
        exit()

print("OK")