//#inlude<bits/stdc++.h> //usig namespace std; //it mai() //{ //flat a,b,x,y; //cin >> x >> a >> y >> b //float z=(b*ya*x)/(b-a); //cout<<fixed << setprecision(2) <<; //retrn 0; //} #include<bits/stdc++.h> using namespace std; int main() { float a,b,x,y; cin >> x >> a >> y >> b ; float z=(b*y-a*x)/(b-a); cout<<fixed << setprecision(2) <<z; return 0; }