function All_repl(unused::Array, prefix::Array, iteration::Int64, length::Int64)
        result = []

    if iteration == 1
        #print(prefix)
        return prefix
    else
        for i in unused
            x = All_repl(delete(unused, i), add(prefix, i), iteration - 1, length)
                if iteration == 2
                    push!(result, x)

                else
                    append!(result, x)
                end

        end
            return result
    end
end