set /a APPEND_CTR=0

for /L %%i in (1,1,%IN_PARTS%) do (
  set /a ctr_tmp=!APPEND_CTR!
  if !APPEND_CTR! EQU 0 (
    set IN_APPEND_!ctr_tmp!="!IN_APPEND_BASE!%%i.mkv"
    set V_OPTS_APPEND_!ctr_tmp!=%V_OPTS_PRI%
  ) else (
    set IN_APPEND_!ctr_tmp!="+!IN_APPEND_BASE!%%i.mkv"
    set V_OPTS_APPEND_!ctr_tmp!=!V_OPTS_SEC!
    set V_APP_TIDLIST=!V_APP_TIDLIST_TMP!
  )
  set V_APP_TIDLIST_TMP=%%i:1:!ctr_tmp!:1
  set /a APPEND_CTR=!APPEND_CTR!+1
  if !APPEND_CTR!==!IN_PARTS! (
    goto :append_loop_end
  )
)

:append_loop_end
set APPEND_TR_OPTS=%V_OPTS_APP% %V_APP_TIDLIST%

set /a ctr_beg=0
set /a ctr_end=%APPEND_CTR%-1

for /L %%i in (%ctr_beg%,1,%ctr_end%) do (
  set /a ctr_tmp=%%i
  if !ctr_tmp! EQU 0 (
    set APPEND_MUX_OPTS=!V_OPTS_APPEND_%%i! !IN_APPEND_%%i!
    set APPEND_LIST=!IN_APPEND_%%i!
  ) else (
    set APPEND_MUX_OPTS=!APPEND_MUX_OPTS! !V_OPTS_APPEND_%%i! !IN_APPEND_%%i!
    set APPEND_LIST=!APPEND_LIST!!IN_APPEND_%%i!
  )
)

SET APPEND_LIST=%APPEND_LIST:"=%
SET APPEND_LIST=%APPEND_LIST:+=,%
goto :append_mux