#define _CRT_SECURE_NO_WARNINGS

#include <algorithm>
#include <iostream>
#include <set>
#include <string>
#include <vector>


using namespace std;

typedef long long int ll;

#define REP(i,n) for(ll i=0; i<=n; ++i )
#define REPR(i,n) for( ll i=n; i>=0; --i)
#define FOR(i,a,n) for(ll i=a; i<=n; ++i )
#define FORR(i,a,n) for(ll i=n; i>=a; --i)

#define VDOUT(x) cerr << #x << "\n";for(auto i : x ) cerr << "  " << i << "\n";
#define DOUT(x) cerr << #x << " = " << x << "\n";

#define COUT(x) cout << x << "\n";
#define COUT2(x,y) cout <<x << " " << y << "\n";
#define COUT3(x,y,z) cout <<x << " " << y << " " << z << "\n"; 

#define INI ios::sync_with_stdio(false);cin.tie(0)


#define ALL(x) x.begin(),x.end()



int main()
{
	INI;

	double b1, b2, b3, b4;
	cin >> b1 >> b2 >> b3;
	b4 = (b3 - b2) / (b2 - b1)*b3 + b2 - (b3 - b2) / (b2 - b1)*b1;
	COUT(b4);

	return 0;
}