# coding: utf-8
import array, bisect, collections, copy, heapq, itertools, math, random, re, string, sys, time
sys.setrecursionlimit(10 ** 7)
INF = 10 ** 20
MOD = 10 ** 9 + 7


def II(): return int(input())
def ILI(): return list(map(int, input().split()))
def IAI(LINE): return [ILI() for __ in range(LINE)]
def IDI(): return {key: value for key, value in ILI()}


def read():
    b_1, b_2, b_3 = ILI()
    return b_1, b_2, b_3


def solve(b_1, b_2, b_3):
    ans = (b_3 - b_2) ** 2 // (b_2 - b_1) + b_3
    return ans


def main():
    params = read()
    print(solve(*params))


if __name__ == "__main__":
    main()