A = input()
B = input()
for r in A + B:
    if "0" <= r <= "9":
        True
    else:
        print("NG")
        exit(0)
if (A != "0" and A[0] == "0") or (B != "0" and B[0] == "0"):
    print("NG")
else:
    if 0 <= int(A) <= 12345 and 0 <= int(B) <= 12345:
        print("OK")
    else:
        print("NG")