#include<cstdio>
#include <iostream>
#include<algorithm>
#include<string>
#include<queue>
#include<vector>
#include<functional>
#include<cmath>
#include<map>
#include<stack>
#include<set>
#include<numeric>

#define mod 1000000007;

using namespace std;
typedef long long ll;
typedef pair<ll, ll> Pr;

ll b1, b2, b3;

int main()
{
	cin >> b1 >> b2 >> b3;
	double r = ((double)(b2-b3)/(b1 - b2));
	double d = -r*b1 + b2;
	printf("%lld\n",(ll)(r*b3+d));
	return 0;
}