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

solver = function(n)
    local t, p, j
    
    t = {}
    p = {}
    
    for i = 1, n + 2 do
        t[i] = 0
    end
    
    t[1] = 1
    p[1] = true
    
    for i = 1, n do
        if p[i] then
            j = i + 1
            t[j] = t[j] + t[i]
            p[j] = true
            j = j + 1
            t[j] = t[j] + t[i]
            p[j] = true
        end
    end
    
    return t[n + 1]
end

main = function()
    local n = io.read()
    local ans = solver(n)
    print(ans)
end

main()