function rot13(s)
local a = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
local b = "NOPQRSTUVWXYZABCDEFGHIJKLMnopqrstuvwxyzabcdefghijklm"
return (s:gsub("%a", function(c) return b:sub(a:find(c)) end))
end
