# Here your code !
n,k = gets.chomp.split(" ").map(&:to_i)
t = gets.chomp.split("").map(&:to_i)
a = 0
b = 0
c = 0
t.each do |d|
    if(b >= k)
        puts a
        exit
    end
    b += 1
    if(c > 0)
        c -= 1
    else
        a += 1
    end
    c += d
end
r = 0
t.each do |d|
    if(c > 0)
        c -= 1
    else
        r += 1
    end
    c += d
end
m = k - b
a += m * r / n
b += a * n
t.each do |d|

    b += 1
    if(c > 0)
        c -= 1
    else
        a += 1
    end
    c += d
        if(b >= k)
        puts a
        exit
    end
end
puts a