#include <bits/stdc++.h>
#include "bits/stdc++.h"
#include <iostream>
#include <iomanip>
#include <vector>
#include <algorithm>
#include <string>
#include <sstream>
#include <cmath>
#include <stack>
#include <queue>
#include <cctype>
#include <stdio.h>
#include <map>
#include <unordered_map>
#include <string.h>
#include <utility>

typedef long long ll;
const int INF = 1e8;

#define rep(i,n) for(ll i=0;i<(ll)(n);i++)
using namespace std;

typedef pair<int, int> P;


int main() {


	long long b1=0,b2=0,b3=0;

	cin>>b1>>b2>>b3;

/*	int r = (b2-b3)/(b1-b2);
	int d = b2-r*b1;*/

	cout<<(b3 - b1) * (b3 - b2) / (b2 - b1) + b2<<endl;
	return 0;
}