#include<string>
#include<vector>
#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<stack>
#include<queue>
#include<cmath>
#include<algorithm>
#include<list>
#include<set>
#include<map>
#include<cstring>
#include<sstream>
#include<cassert>
#define rep(X,Y) for (int (X) = 0;(X) < (Y);++(X))
#define reps(X,S,Y) for (int (X) = S;(X) < (Y);++(X))
#define rrep(X,Y) for (int (X) = (Y)-1;(X) >=0;--(X))
#define repe(X,Y) for ((X) = 0;(X) < (Y);++(X))
#define peat(X,Y) for (;(X) < (Y);++(X))
#define all(X) (X).begin(),(X).end()

using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;

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