import sys; input = sys.stdin.buffer.readline
sys.setrecursionlimit(10**7)
from collections import defaultdict
con = 10 ** 9 + 7; INF = float("inf")
from math import gcd

def getlist():
	return list(map(int, input().split()))

#処理内容
def main():
	b1, b2, b3 = getlist()
	ans = int(((b3 - b2) ** 2) // (b2 - b1)) + b3
	print(ans)

if __name__ == '__main__':
	main()