v = input()
v = v.split(" ")
v = [float(i) for i in v]
d = float(input())
runspeed = float(input())

length = 0

for i in range(100):
    time1 = d/(v[1]+runspeed)
    plus1 = time1 * runspeed
    d = d - time1*(v[0]+v[1])
    time2 = d/(v[0]+runspeed)
    plus2 = time2 * runspeed
    d = d - time2*(v[0]+v[1])
    length = length+(plus1+plus2)
    if plus1<=10**(-6):
        break
print(length)