n,e = map(int,input().split())
a = list(map(int,input()))
buy = 0
count = 0
bonus = 0
for i in range(e):
    if count == e:
        break
    for j in range(n):
        count += 1
        if bonus == 0:
            buy +=1
        else:
            bonus -= 1
        bonus += a[j]
        if count == e:
            break
print(buy)