b1, b2, b3 = map(int, input().split())

b3 - b2 / b2 - b1
b2 ** 2 - b1 * b3 / b2 - b1

print((b3 * (b3 - b2) + (b2 ** 2 - b1 * b3 )) // (b2 - b1))