# なぜ自分のコードはこんなに長いのか(´・ω・｀)

N, K = gets.split.map(&:to_i)
S = gets.chomp

def calc(want, kuji)
  raise unless want > 0

  buy = 0
  for i in 0...N do
    if kuji > 0 then
      kuji -= 1
    else
      buy += 1
    end
    kuji += S[i].to_i
    want -= 1
    break if want <= 0
  end
  return buy, kuji
end

buy_sum = 0
want = K

buy_prev = nil
kuji_prev = 0
while want > 0 do
  buy, kuji = calc(want, kuji_prev)
  break if buy <= 0 && kuji >= kuji_prev #クジだけでやっていける
  if buy == buy_prev && kuji == kuji_prev then #パターンに入った
    q, r = want.divmod(N)
    buy_sum += buy * q
    want = r

    if want > 0 then
      buy, kuji = calc(want, kuji_prev)
      buy_sum += buy
      want -= N
    end
  else
    buy_sum += buy
    want -= N
  end

  buy_prev = buy
  kuji_prev = kuji
end

puts buy_sum