Explain CDRN02 problem


#1

Contest is over can someone explain this https://www.codechef.com/COON2019/problems/CDRN02 problem.
for the test case provided i understood when A army fort is 3x3 and B army attacks like this in 2x2 .

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output : 4

if i considered B army is 2x2 again and the A army fort is 4x4.
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then the output would be 4 right ?

but why the answer is 9 i mean it would be like this

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if this would be answer why the problem tester didnt provide another test case or explain it well if so many beginners like me would had understand .


#2

The problem was not explained well at all.


#3

you mean the question in the contest?