#include <iostream>
using namespace std;

double Calc(double,double);

int main() {
   double a,b;
   cout<<"a= ";
   cin>>a;
   cout<<"b= ";
   cin>>b;
   cout<<"Result: "<<Calc(a,b)<<endl;

    system ("pause");
    return 0;
}
double Calc(double a, double b){
    double x;
    x = 2*((a−b)/(b−a));
    return x;
}