we should select the proper range otherwise the list becomes out of order, but in this example no need(can select range(0, n))

def birthday(s, d, m, n):
  count = 0
  for i in range(n-m+1):
    if(sum(s[i:m+i])==d):
        count = count + 1
  return count

Any quasions, fell free to ask.