题解 | 字符串注意连续子串是至少为M不是只能为M

n, m = map(int, input().split())
s = input()
count = ans = 0
for i in range(n):
    if s[i] == "1":
        count += 1
    else:
        a = count - m + 1
        if a > 0:
            ans += (1 + a) * a // 2
        count = 0
a = count - m + 1
if a > 0:
    ans += (1 + a) * a // 2
print(ans)