Trying to use "else" statment in batch

I pretty new to this but if anyone could help me out on why this is not working if I dont put in the correct number. Here is my section of code that is going wrong:

:veri                                                         
cls              
echo Conformation step repeat this number: %RANDOM%  
set /p a=  
if %a%==%RANDOM% goto tv   
else goto fail