A 100 B 200 B 300 C 400 D 500 C 600 D 700 ..etc.

##</code><code>##

A 100 -> seqno = 1, 
B 200 -> seqno = 1, 
B 300 -> seqno = 2, 
C 400 -> seqno = 1, 
D 500 -> seqno = 1, 
C 600 -> seqno = 2,
D 700 -> seqno = 2, etc.