my intention is to keep the code as simple as possible.Here there are 5 files namely 

`A_1.CSV, A_2.CSV, A_3.CSV, A_4.CSV, A_5.CSV` 

The below code retrieves the first row in a CSV file.
 
Code : head.sh(filename)

 awk -F, 'NR==1 {print $0}' A_1.CSV > Header.csv
 awk -F, 'NR==1 {print $0}' A_2.CSV >> Header.csv
 awk -F, 'NR==1 {print $0}' A_3.CSV >> Header.csv
 awk -F, 'NR==1 {print $0}' A_4.CSV >> Header.csv
 awk -F, 'NR==1 {print $0}' A_5.CSV >> Header.csv

Question :

In the above code, only the filename changes from A_1 to A_2 and so on. How can I make the code simple with loops.

Example :

 for (i=1;i<=5;i++)
 {
 A_[i].CSV >> Header.csv
 }

I don't know how to do this logic with shell scripting.
Thank You