from math import factorial


n = int(input())
x = float(input())

s = 1           # complex sum
k = 1           # exponent of x
factorial = 1

for i in range(1, n + 1):
    factorial = factorial * i
    s = s + (factorial / x ** k)
    k = k + 1
    if k == n + 1:
        break

print(f'{s:.5f}')