list_filter.ex

defmodule Solution do
    def main do
        String.split(IO.read(:stdio, :all), [" ", "\n"])
        |> Enum.with_index 
        |> Enum.filter(fn({_,i}) -> rem(i,2) ==1 end) 
        |> Enum.map(fn({x,_})->x end)
        |> Enum.join("\n") 
        |> IO.puts

    end
end
Solution.main

Enum.map(&String.to_integer/1)