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

total = 1
count = 1
(0...N).each{|i|
    if count == 0
        count +=1
        total +=1
        #puts "i=#{i}, total=#{total}"
    end

    count -=1
    count += S[i].to_i
    if i>=k
        puts total
        exit
    end
    
}
#puts "1:total=#{total}, count=#{count}, k=#{k}, N=#{N}"
k -= N
su = S.split('').map(&:to_i).inject(&:+)
#puts "su=#{su}"
if su > S.length
    count += (k/N) * (su - S.length )
else
    total += (k/N) * (S.length - su)
end
    k%=N
#uts "2:total=#{total}, count=#{count}, k=#{k}, N=#{N}"

(0...k).each{|i|
    if count == 0
        count +=1
        total +=1
        #puts "i=#{i}, total=#{total}"
    end
    count -=1
    count += S[i].to_i
    if i>=k
        puts total
        exit
    end
    
}
puts total