Guys help please!!!

I'm having trouble with my %ctr% dont know if its the right code for this
what I'm looking is if you multiply 7 to 7 the output should come to this:

1 x 7=7
2 x 7=14
3 x 7=21
4 x 7=28
5 x 7=35
6 x 7=42
7 x 7=49

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this is my code:

@echo off

:start

set /p i=insert a number:
set /p a=multiplied times:
goto multi

:multi
set /a ctr=%ctr%+1 -->problem
set /a pro=%i%*%a%
echo %i% x %a%=%pro%
pause

goto start

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thanks Guys :)