CodeForces Round #650 div3

Problem: 1376C Social Distance
https://codeforces.com/contest/1367/problem/C

My Code link: https://ideone.com/Dt76cw

My Approach : I first create a prefix sum array of the given string . Then starting from 1st index say ‘i’ I do a upper_bound operation with prefix_arr[i] value, which gives me the index of postion of 1 occuring after the postion ‘i’.Call it ‘j’ and all the characters in between ‘i’ and ‘j’ are the number of 0. I have also taken in mind the calculation of zeros for the corner cases.
After getting the number of zeroes I subtract ‘k’ from it 2 time or 1 time depending on the position of ‘i’ and ‘j’ . Then I divide the number of zeroes by k+1 and increment the count by this value. Also if the there is any remainder >=1 ,it is also increments the count.
Then I update the value of i as the psotion ‘j’ and continue looping.
Please help me and tell what is wrong with my code.

WA in case of 5 2 10000
the case in which no k needs to be subtracted is not handled according to me

no i have. This will be the case if the whole string consists of zeroes.
so i simply just divide n/(k+1) and check if there is any remainder.

in case of
1
5 2
10000
your answer:2
correct answer:1