#include <bits/stdc++.h>
 
using namespace std;

int main(void) 
{
  cin.tie(0);
  ios::sync_with_stdio(false);

  long long int b1,b2,b3;

  cin >> b1 >> b2 >> b3;

  long long int A = b3 - b2;
  long long int B = b2 - b1;

  long double r = (A*1.0/B);
  long double d = b2 - r*b1;
  cout << (long long int)(r*b3 + d) << '\n';

  return 0;
}