#include <iostream>
#include <stdio.h>
#include <string>
#include <vector>
#include <cmath>
#include <algorithm>
#define MP make_pair
using ll = long long;
using namespace std;

int main()
{
  double b1,b2,b3;
  cin >> b1 >> b2 >> b3;
  double r = (b3-b2) / (b2-b1);
  double d = b2-r*b1;
  cout << r*b3 + d << endl;
  return 0;
}