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Please explain what the problem is.

For the 3 lines you've shown:
set cnt=3
set change to -2
print cnt Qs
cnt = cnt + change
print cnt Qs
now set change to +2 -> to add 2 to cnt instead of...

Can you explain what the problem is printing the third line? For that simple example the third line is the same as the first line.
Look at the post#3. Think about how the line lengths shorten and...