XSL - sum multiplication of elements

Question

I have a few items like this one:

    172
    42         


        

Answer 1

XSLT:

  

  
    sum:

    
      
    
  

  
    
    

    

     
      
        
        
      
    

    
      
    

  

Input XML:

  
    1
    2
    7
  
  
    10
    20
    7
  
  
    100
    200
    7
  

Output:

sum:20202