Capgemini Mainframe Real Time Scenario Based Interview Question. 

Input file consist of product id and it can repeat multiple times so we need to write sequence no for every record of product id. Whenever product id changes we need to reset the sequence to 1 again.
Input file data
A001
A001
A001
B003
B003
Output file data.
_______
A001 1
A001 2
A001 3
B003 1
B003 2