A,B = list(map(int,input().split()))

if A<=9 and B<=9:

    print((A*B))

else:

    print((-1))
A,B = list(map(int,input().split()))

if 1<=A<=9 and 1<=B<=9:

    print((A*B))

else:

    print((-1))
A, B = list(map(int, input().split()))
if A <= 9 and B <= 9:
    print((A * B))
else:
    print((-1))

A, B = list(map(int, input().split()))
if 1 <= A <= 9 and 1 <= B <= 9:
    print((A * B))
else:
    print((-1))

-if A <= 9 and B <= 9: +if 1 <= A <= 9 and 1 <= B <= 9: