#include <bits/stdc++.h>
#define REP(i,n,N) for(int i=(n);i<(int) N;i++)
#define RREP(i,n,N) for(int i=N-1;i>=(int) n;i--)
#define p(s) cout<<(s)<<endl
#define DEBUG(x,y) cout<<#x<<": "<<x<<" , "<<#y<<": "<<y<<endl;
#define CK(n,a,b) ((a)<=(n)&&(n)<=(b))
#define F first
#define S second
typedef long long ll;
using namespace std;
const ll inf=1e9;


int main(){
	ll x, y, z;
	cin>>x>>y>>z;

	p(y+(z-x)*(z-y)/(y-x));

	return 0;
}