#include <algorithm>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <functional>
#include <iostream>
#include <iterator>
#include <limits>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <utility>
#include <valarray>
#include <vector>

#define MOD 1000000007
#define pe(str) return cout<<(str)<<endl,0
#define px(str) {cout<<(str)<<endl;exit(0);}
#define pr(str) cout<<(str)<<endl
#define prpr(str) cout<<str<<endl
#define db(str) cerr<<(str)<<endl
#define dbdb(str) cerr<<str<<endl
#define re(i,n) for(int i=0;i<(n);i++)
#define rep(i,a,b) for(int i=(a);i<(b);i++)
#define bw(a,b,c) (((a)<=(b))&&((b)<=(c)))
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef pair<int,int> pii;

template<class InputIterator>
void dump(InputIterator first,InputIterator last,char delim=' '){
	for(InputIterator it=first;it!=last;it++){
		if(it!=first)cout<<delim;
		cout<<*it;
	}
}

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