#include <cstdio>
#include <cstdlib>
#include <iostream>
#include <string>
#include <cmath>
#include <algorithm>
#include <vector>
#include <queue>
#include <stack>
#include <map>
#include <set>
#include <cstring>

typedef long long ll;
using namespace std;

#define mod 1000000007
#define INF 1000000000 //(int)1e9
#define LLINF 2000000000000000000 //(ll)2e18
#define PI  3.1415926536

#define SIZE 100000

int main(){
    int a,b,x,y;
    double ans=0;
    
    // a:b = x1:y1
    // b*x1 = a*y1
    
    
    
    cin >> a >> b >> x >> y;
    
    if(b*x < a*y){
        ans = (double)x+((double)b*x/a);
    }else{
        ans = (double)y+((double)a*y/b);
    }
    
    printf("%.15lf\n",ans);
    
    return 0;
}