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)