n, k = gets.split.map(&:to_i)
s = gets.strip
a = Array.new
b = Hash.new(-1)
s.each_char{ |x| a.push(x.to_i) }
buy = 0
curr = 0
count = 0
while true do
    if b.has_key?(curr)
        break
    end
    buy += 1
    free = 0
    roop = curr
    pc = 0
    while true do
        free += a[curr]
        count += 1
        pc += 1
        break if free == 0
        curr = (curr + 1) % n
        free -= 1
        break if roop == curr
    end
    if count >= k || (a[roop] != 0 && roop == curr)
        puts buy
        exit
    end
    b[roop] = pc
    curr = (curr + 1) % n
end
bn = 0
kc = 0
find = false
vsum = 0
b.each do |key, value|
    if key == curr
        bn = b.length - kc
        find = true
    end
    if find
        vsum += value
    end
    kc += 1
end
rc = (k - count) / vsum
left = k - count - rc * vsum
buy += rc * bn
vc = 0
b.each_value do |value|
    if vc >= b.length - bn
        if left <= 0
            break
        end
        left -= value
        buy += 1
    end
    vc += 1
end
puts buy