N, K = map(int, raw_input().split())
S = raw_input()

ans = 0
free = 0
eaten = 0

while True:
    for i in xrange(len(S)):
        if free > 0:
            free -= 1
        else:
            ans += 1

        eaten += 1
        free += int(S[i])

        if eaten == K:
            print ans
            exit()
    if free > 0:
        print ans
        exit()