#include <algorithm>
#include <cstdio>
#include <iostream>
#include <map>
#include <cmath>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>
#include <stdlib.h>
#include <stdio.h>
#include <bitset>
using namespace std;
#define FOR(I,A,B) for(int I = (A); I < (B); ++I)
typedef long long ll;

int main(){
  int A,B,X,Y;
  cin>>A>>B>>X>>Y;
  double ansy = double(B*X)/A;
  double ansx = double(A*Y)/B;
  if(ansy > Y) ansy = -100000;
  if(ansx > X) ansx = -100000;
  if(ansy + X >= ansx + Y){
    printf("%.07lf\n", ansy + X);
  } else {
    printf("%.07lf\n", ansx + Y);
  }
  return 0;
}