Problem with code (PIBRO)

problem link:

can anyone please provide a test-case for which my code fails.currently showing WA.

code:
https://www.codechef.com/viewsolution/28013706

Consider the testcase:

1
9 6
010000001

Answer should be 8:

Longest consecutive run of 1's = 8 obtained by changing the following marked range (of size 6) to all 1's: 
010000001
  ^    ^
Giving: 
011111111