defmodule Main do
  def main do
    s = IO.gets("") |> String.trim() |> String.codepoints()
    t = IO.gets("") |> String.trim() |> String.codepoints()

    checkarray(s, t, 0)
    |> IO.puts()
  end

  defp checkarray([s_head | []], [t_head | []], count) do
    if s_head == t_head do
      count
    else
      count + 1
    end
  end

  defp checkarray([s_head | s_rest], [t_head | t_rest], count) do
    if s_head == t_head do
      checkarray(s_rest, t_rest, count)
    else
      checkarray(s_rest, t_rest, count + 1)
    end
  end
end