def gcd(x,y):
  if y == 0: return x
  return gcd(y,x%y) 

n = input()
c = [4,3]
p = [1,1]
for i in xrange(n-1):
  c.append(19*c[i+1]*p[i] - 12*c[i]*p[i+1])
  p.append(4*p[i+1]*p[i])
  g = gcd(c[i+2],p[i+2])
  c[i+2] /= g
  p[i+2] /= g
  #print c[i], p[i]
print "%.10f" % (1.0*c[n]/p[n])