/*
 * 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;

  cin >> b1;
  cin >> b2;
  cin >> b3;

  cout <<  b3*(b3 - b2) / (b2 - b1) + b2 - (b3 - b2) / (b2 - b1) * b1 << endl;

  return 0;
}