from functools import lru_cache

@lru_cache(maxsize = None)
def comb(n, k):
  if k == 0 or k == n:
    return 1
  else:
    return comb(n-1, k-1) + comb(n-1, k)

@lru_cache(maxsize = None)
def B(n):
  if n == 0:
    return 1
  else:
    return -sum(comb(n+1, k) * B(k) for k in range(0, n)) / (n+1)

def solve(x, N = 100, K = 100):
  S  = sum((x+n)**(-2) for n in range(1, N+1))
  S += 1/(x+N) - 0.5/(x+N)**2
  S += sum(B(2*k)*(x+N)**(-2*k-1) for k in range(1,K+1))
  return S

x = float(input())
print(solve(x))