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

for i in range(100000):

    if int(i*0.08)==A and int(i*0.1)==B:

        print(i)

        break

else:

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

for i in range(10**4+100):

    if int(i*0.08)==A and int(i*0.1)==B:

        print(i)

        break

else:

    print((-1))

A, B = list(map(int, input().split()))
for i in range(100000):
    if int(i * 0.08) == A and int(i * 0.1) == B:
        print(i)
        break
else:
    print((-1))

A, B = list(map(int, input().split()))
for i in range(10**4 + 100):
    if int(i * 0.08) == A and int(i * 0.1) == B:
        print(i)
        break
else:
    print((-1))

-for i in range(100000): +for i in range(10**4 + 100):