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%;"/>.
# MC621 - Desafios de Programacao II - 2s2020
# Problema G: Archer

# utiliza split para possibilitar a leitura das 3 variaveis
a, b, c, d = input().split()

# converte os valores das variaveis para int 
a, b, c, d = int(a), int(b), int(c), int(d)

# calculo da probabilidade
"""
- a formula fechada se da considerando as probabilidades e seus respectivos complementos
- nos levando a uma soma dos termos de uma PG infinita
  S = a/(1-r)
- sendo
  'a', a probabilidade de acerto a/b
  'r', o complemento de a/b vezes o complemento de c/d
"""
prob = a/b/(1-(1-a/b)*(1-c/d))

# impressao do resultado
print(round(prob, 12))
     			         	  		 	   		