#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <map>
#include <set>
#include <cstdio>
#include <cmath>
#define rep(i,l,n) for(int i=l;i<n;i++)
#define rer(i,l,n) for(int i=l;i<=n;i++)
#define all(a) a.begin(),a.end()
#define o(a) cout<<a<<endl
#define pb(a) push_back(a)
#define mk(a,b) make_pair(a,b)
#define fi first
#define se second
using namespace std;
typedef long long lint;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef pair<int,int> pii;

int main(){
	double a,b,x,y,ans1=0,ans2=0;
	cin>>a>>b>>x>>y;
	if(b/a*x<=y) ans1=(1+b/a)*x;
	if(a/b*y<=x) ans2=(1+a/b)*y;
	printf("%.8lf\n",max(ans1,ans2));
}