#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#define loop(i,a,b) for(i=a;i<b;i++)
#define rloop(i,a,b) for(i=a;i>=b;i--)
#define vi vector<int>
#define vl vector<ll>
#define vii vector< vector<int> >
#define vll vector< vector<ll> >
#define vs vector<string>
#define pii pair<int,int>
#define psi pair<string,int>
#define pis pair<int,string>
#define pss pair<string,string>
const int inf=1000000001;
const ll INF=1e16;
#define MOD 1000000007
#define mod 1000000009
#define pi 3.14159265358979323846
#define Sp(p) cout<<setprecision(15)<<fixed<<p<<endl;

int main(){
  double a,b,c;
  cin>>a>>b>>c;
  if(a==b){
    cout<<a<<endl;
  }else{
    cout<<((b*c - c*c + a*c - b*b) / (a - b))<<endl;
  }
}