/*
 * 538.cpp
 */

//include files
#include<bits/stdc++.h>

using namespace std;

//DEFINE MACROS
#define MIN(a,b) (a>b?b:a)
#define MAX(a,b) (a>b?a:b)
#define PRINTLN(s) cout << s << endl

//DEFINE CONSTANT

//DEFINE PROTOTYPE

int main(){
  long long int b1,b2,b3;
  double r,d;
  long long int answer;

  cin >> b1;
  cin >> b2;
  cin >> b3;
  r = (double) (b3 - b2) / (b2 - b1);
  d = b2 - r * b1;
  answer = b3*r + d ;
  cout << answer << "\n";

  return 0;
}