from decimal import Decimal

def main():
	b1, b2, b3 = list(map(int, input().split(' ')))
	if b1 == b2: return b1
	r = Decimal(b2 - b3) / Decimal(b1 - b2)
	d = Decimal(b3 * b1 - b2 ** 2) / Decimal(b1 - b2)
	return int(r * b3 + d)

print(main())