Recursion error for a algorithmic problem

I was trying to do the question- First negative integer in every windows of size k from a array (b) of size n.
I tried using recursion but the below error came. I am trying to figure out but didn’t get my mistake. Please look into the code below

ans = []
def fnc(b,n,k):
    global ans
    dq = []
    
    for i in range(0,k):
        if b[i]<0:
            dq.append(b[i])
    if len(dq) != 0:
        ans.append(dq[0])
    else:
        ans.append(0)
        
    dq = []
    b.remove(b[0])
    bnew = b
    nnew = len(bnew)  # or nnew = n-1
    
    while len(bnew) > 1:
        fnc(bnew,nnew,k)

input:
B = [12, -1, -7, 8, -15, 30, 16, 28]
N = 8
K = 3
fnc( B, N, K)
print(ans)

Showing error List Index out of range

>Solution :

The problem is that you are recursively removing the first element of B, so in the run you will encounter the state where len(b) < k, so I would recommend to change the while loop to :

while len(bnew) > k:
   fnc(bnew,nnew,k)