x = float(input())
summary = 1
eps = 0.001

stepper = 2
enumerator = x
denomerator = 1.0

while True:
    temp = enumerator / denomerator
    summary += temp

    enumerator *= x
    denomerator *= stepper
    stepper += 1

    if abs(temp) < eps:
        break

print(summary)