local function rot13(s)
    local bytes = {s:byte(1,  #s)}
    for i = 1, #bytes do
        local c = bytes[i]
        if (c >= 65 and c <= 77) or (c >= 97 and c <= 109) then
            bytes[i] = c + 13
        elseif (c >= 78 and c <= 90) or (c >= 110 and c <= 122) then
            bytes[i] = c - 13
        end
    end
    return string.char(bytes:unpack())
end

print(rot13("nowhere ABJURER"))