set /a a0=0,b=0,c=1,e=1
for /f "delims=: tokens=1*" %%i in ('findstr /n .* in.txt') do (
set "a%%i=%%j"
if defined a%%i set /a b=%%i
set /a c=%%i+1
)
setlocal enabledelayedexpansion
if not "!a%b%!"=="!a%b%:hoge=!" set /a c=b
set "a%c%=hoge"
del out.txt
:y
echo.!a%e%!>>out.txt
set /a e+=1 & if !e! leq !c! goto y