>>913
set s=abcdefg
setlocal enabledelayedexpansion
set n=0 & if defined s (set /a "n=1<<13"
for /L %%i in (12,-1,0) do (set /a "a=n-(1<<%%i)"
for %%j in (!a!) do if "!s:~%%j,1!"=="" set n=!a!))
echo !n!