-- yukicoder My Practice
-- author: Leonardone @ NEETSDKASU

n = io.read()

t = {}
p = {}

t[1] = 1
p[1] = 1

repeat
	local s, c
	s = {}
	c = 0
	for i = 1, n + 1 do
		if p[i] ~= nil then
			if t[i + 1] == nil then t[i + 1] = 0 end
			if t[i + 2] == nil then t[i + 2] = 0 end
			t[i + 1] = t[i + 1] + t[i]
			t[i + 2] = t[i + 2] + t[i]
			p[i + 1] = 1
			p[i + 2] = 1
			c = c + 1
		end
	end
	p = s
until c == 0

print(t[n + 1])