a = input()
b = input()
try:
    A = int(a)
    B = int(b)
except:
    exit(print("NG"))
if A == 0:
    if len(a) >= 2:
        exit(print("NG"))
if B == 0:
    if len(a) >= 2:
        exit(print("NG"))
if (A > 0 and a[0] == "0") or (B > 0 and b[0] == "0"):
    exit(print("NG"))
try:
    assert(0 <= A <= 12345)
    assert(0 <= B <= 12345)
except:
        exit(print("NG"))
print("OK")