#include<bits/stdc++.h>

using namespace std;
using ll=long long;
#define rep2(i, a, n) for(int i = (a); i < (n); i++)
#define rep(i, n) rep2(i,0,n)

int main(){
  cin.tie(nullptr);ios_base::sync_with_stdio(false);
  cout<<fixed<<setprecision(15);
  double a,b,x,y;
  cin>>a>>b>>x>>y;
  cout<<(a+b)*min(x/a,y/b)<<endl;
}