defmodule M do

    def mingle(l1, l2) do
        mingle(l1, l2, "")
    end

    def mingle([], [], str), do: IO.puts str

    def mingle([h1 | t1], [h2 | t2], str) do
        mingle(t1, t2, str <> h1 <> h2)
    end

    def main() do 
        l1 = IO.gets("") |> String.trim |> String.codepoints
        l2 = IO.gets("") |> String.trim |> String.codepoints
        mingle(l1, l2)
    end
end

M.main