def count_substrings(n, arr, k):
    l, z, o, res = 0, 0, 0, 0
    for r in range(n):
        if arr[r] == '0':
            z += 1
        else:
            o += 1
        while z > k or o > k:
            if arr[l] == '0':
                z -= 1
            else:
                o -= 1
            l += 1
        res += r - l + 1
    return res

def main():
    n = int(input().strip())
    arr = input().strip()
    k = int(input().strip())
    if k == 0:
        print(0)
    else:
        print(count_substrings(n, arr, k))

if __name__ == "__main__":
    main()

def maxResourceValue(n, m, grid):
    dp = [[0] * m for _ in range(n)]

    for i in range(n):
        for j in range(m):
            if grid[i][j] == -1 or grid[i][j] == -3:
                dp[i][j] = 0
            elif i == 0 and j == 0:
                dp[i][j] = grid[i][j] if grid[i][j] > 0 else 0
            else:
                top = dp[i - 1][j] if i > 0 else 0
                left = dp[i][j - 1] if j > 0 else 0
                dp[i][j] = max(top, left) + (grid[i][j] if grid[i][j] > 0 else 0)

    return dp[n - 1][m - 1]

def main():
    n, m = map(int, input().strip().split())
    grid = []
    for _ in range(n):
        row = list(map(int, input().strip().split()))
        grid.append(row)

    result = maxResourceValue(n, m, grid)
    print(result)

if __name__ == "__main__":
    main()