EWWWWWW

c = function(txt)
    local x = string.reverse(txt)
    local nt = ""
    local s = false
    for i = 1,#txt do
        if not s then
            s = true
            nt = nt..string.sub(x,i+1,i+1)
        else
            s = false
            nt = nt..string.sub(x,i-1,i-1)
        end
    end
    if #x%2~=0 then
        nt = nt..string.sub(x,#x,#x)
    end
    return nt
end