SmallR is an archer. SmallR is taking a match of archer with Zanoes. They try to shoot in the target in turns, and SmallR shoots first. The probability of shooting the target each time is <img align="middle" class="tex-formula" src="https://espresso.codeforces.com/a7487d7e62f90136b78ae3fbf0a008396f146e13.png" style="max-width: 100.0%;max-height: 100.0%;"/> for SmallR while <img align="middle" class="tex-formula" src="https://espresso.codeforces.com/c443c7703e51f03d0eece0b96b9e84e425878209.png" style="max-width: 100.0%;max-height: 100.0%;"/> for Zanoes. The one who shoots in the target first should be the winner.

Output the probability that SmallR will win the match.
A single line contains four integers <img align="middle" class="tex-formula" src="https://espresso.codeforces.com/488158367221f441ba94b9475c03436069df2a7e.png" style="max-width: 100.0%;max-height: 100.0%;"/>.
from heapq import *
from queue import *
import sys, math, bisect
from collections import OrderedDict
from collections import Counter, defaultdict
from string import *

input = lambda: sys.stdin.buffer.readline().decode().strip()
# print = sys.stdout.write
inl = lambda: list(map(int, input().split()))


def solve():
    a, b, c, d = inl()

    arch_tries = math.ceil(b / a)
    z_p = (arch_tries - 1) * (c / d)

    print((1 / (1 + z_p)))


solve()
