def main():
	b1, b2, b3 = list(map(int, input().split(' ')))
	if b1 == b2: return b1
	r = (b2 - b3) / (b1 - b2)
	d = (b3 * b1 - b2 ** 2) / (b1 - b2)
	b4 = r * b3 + d
	return int(b4)+1 if b4 - int(b4) > 0.9999999 else int(b4)

print(main())