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

min = Float::INFINITY
max = -Float::INFINITY

cnt = 0

S.each_char do |s|
  cnt -= 1

  case s
  when '1'
    cnt += 1
  when '2'
    cnt += 2
  end
end

def f(x, cnt)
  x += cnt * (K / N)
  r = K % N

  r.times do |i|
    s = S[i]
    x -= 1
    return false if x < 0

    case s
    when '1'
      x += 1
    when '2'
      x += 2
    end
  end

  x >= 0
end

ng = 0
ok = K

while (ok - ng).abs >= 2
  x = (ok + ng) / 2

  if f(x, cnt)
    ok = x
  else
    ng = x
  end
end

puts ok