# (´・ω・｀)
require 'matrix'

n=gets.to_i

if n==0
    p 4
elsif n==1
    p 3
else
    mat = Matrix[[19.0/4,-3.0],[1.0,0.0]]
    u = (mat**n)*Matrix[[3],[4]]
    puts sprintf("%.20f",u[1,0]);
end

# 2 2.25
# 3 1.6875
# 4 1.265625
# 5 0.94921875