from math import factorial


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


s = 1
k = 1
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

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