#!/usr/bin/env python3
#fileencoding: utf-8

A,B,X,Y = [int(i) for i in input().strip().split(" ")]

y = X * B / A
x = Y * A / B

if X >= x and Y >= y:
    print(x+y)
elif X < x and Y >= y:
    print(X+y)
elif X >= x and Y < y:
    print(x+Y)
else:
    if X > Y:
        print(x+Y)
    else:
        print(X+y)