I wrote simple Binary search but got WA#4... Where is my mistake? Maybe there are some special cases... Can you help me, please? Thanks in advance...

I had wa4 and this test helped me to get AC:
6
1 0 1 0 0 1
6
2 2 1
1 1 1
3 3 1
4 4 1
6 6 1
4 5 1
// correct answer is 011010

Try using the STL lower_bound for binary search. It really cuts down potential errors on edge cases.