ConvertText(Text, ByRef OppositeLayout)
{
   Static Cyr := "ЁЙЦУКЕНГШЩЗХЪФЫВАПРОЛДЖЭЯЧСМИТЬБЮ/ёйцукенгшщзхъфывапролджэячсмитьбю,.""№;?:"
        , Lat := "~QWERTYUIOP{}ASDFGHJKL:""ZXCVBNM<>|``qwertyuiop[]asdfghjkl;'zxcvbnm,.?/@#$&^"

   RegExReplace(Text, "i)[A-Z@#\$\^&\[\]'`\{}]", "", LatCount)
   RegExReplace(Text, "i)[А-ЯЁ№]", "", CyrCount)

   if (LatCount != CyrCount)
   {
      CurrentLayout := LatCount > CyrCount ? "Lat" : "Cyr"
      OppositeLayout := LatCount > CyrCount ? "Cyr" : "Lat"
   }
   else
   {
      threadId := DllCall("GetWindowThreadProcessId", Ptr, WinExist("A"), UInt, 0, Ptr)
      landId := DllCall("GetKeyboardLayout", Ptr, threadId, Ptr) & 0xFFFF
      if (landId = 0x409)
         CurrentLayout := "Lat", OppositeLayout := "Cyr"
      else
         CurrentLayout := "Cyr", OppositeLayout := "Lat"
   }
   Loop, parse, Text
      NewText .= (found := InStr(%CurrentLayout%, A_LoopField, 1))
         ? SubStr(%OppositeLayout%, found, 1) : A_LoopField
   Return NewText
}

:?:!шиф::
Input, firs, V, {Enter}
msgbox, ConvertText(%firs%, Layout)