# -*- coding: utf-8 -*-
"""
No.538 N.G.S.
https://yukicoder.me/problems/no/538

"""
import sys
from sys import stdin
input = stdin.readline


def main(args):
    b1, b2, b3 = map(int, input().split())
    r = (b2 - b3) / (b1 - b2)
    d = b2 - r * b1
    print(int(b3 * r + d))


if __name__ == '__main__':
    main(sys.argv[1:])