#include <stdio.h> #include <stdlib.h> #include <iostream> #include <vector> #include <string> #include <queue> #include <algorithm> #include <math.h> #include <utility> #include <set> #include <map> #include <cstring> #include <cstdio> #include <stack> #include <cmath> #define INF 10000000000 #define MOD 10000000007 #define rep(i,n) for(int i =0;i<n;i++) using namespace std; typedef long long int ll; typedef pair<int, int> i_i; int main(){ double a,b,x,y; cin >> a >> b >> x >> y; double ans ; if (x*b/a<=y) { ans = x + x*b/a; }else{ ans = y + y*a/b; } printf("%.6lf\n",ans); }