using System;
using System.Collections.Generic;
using System.Text;

public class Program
{
    public void Proc(){
        Reader.IsDebug = false;
        string[] inpt = Reader.ReadLine().Split(' ');
        this.InBox = int.Parse(inpt[0]);
        this.MustCount = int.Parse(inpt[1]);
        string tmp = Reader.ReadLine();
        this.Map = new int[this.InBox];
        for(int i=0; i<tmp.Length; i++) {
            this.Map[i] = int.Parse(tmp[i].ToString());
        }
        long ans = this.GetAns(0, this.MustCount);
        Console.WriteLine(ans);
    }
    
    Dictionary<int, IceBox> dic = new Dictionary<int, IceBox>();
    
    public long GetAns(int startIdx, long mustBuy) {
        long cnt = 0;
        long ans  = 0;
        int idx = startIdx;
        while (cnt < mustBuy)
        {
            ans++;
            long addCount = 0;
            int subIdx = idx;
            while (cnt + addCount < mustBuy)
            {
                if(dic.ContainsKey(subIdx)) {
                    IceBox bx = dic[subIdx];
                    addCount += bx.AddIce;
                    subIdx = bx.NextIndex;
                    break;
                }
                if(this.Map[subIdx] == 0) {
                    addCount++;
                    subIdx++;
                    break;
                } else if(this.Map[subIdx] == 1)
                {
                    addCount+=1;
                    subIdx+=1;
                } else
                {
                    int tmp = subIdx + 1;
                    if(tmp >= this.Map.Length) {
                        tmp -= this.Map.Length;
                    }
                    if(this.Map[tmp] == 2) {
                        addCount+=3;
                        subIdx += 3;
                    } else
                    {
                        addCount+=2;
                        subIdx+=2;
                    }
                }
                if(subIdx >= Map.Length) {
                    subIdx -= this.Map.Length;
                }
            }
            if(subIdx >= Map.Length) {
                subIdx -= this.Map.Length;
            }
            if(!dic.ContainsKey(idx)) {
                IceBox bx = new IceBox();
                bx.AddIce = addCount;
                bx.BuyAt = idx;
                bx.NextIndex = subIdx;
                dic.Add(idx, bx);
            }
            cnt+=addCount;
            idx = subIdx;
        }
        return ans;
    }
    
    private int[] Map;
    
    private int InBox = 0;
    
    private long MustCount = 0;
    
    public class IceBox {
        public int BuyAt = 0;
        public long AddIce = 0;
        public int NextIndex = 0;
    }
    
    public static void Main(string[] args)
    {
        Program prg = new Program();
        prg.Proc();
    }
   
}

class Reader
{
    public static bool IsDebug = true;
    
    private static System.IO.StringReader sr;
    
    public static string ReadLine() {
        if(IsDebug) {
            if(sr == null) {
                sr = new System.IO.StringReader(initStr.Trim());
            }
            return sr.ReadLine();
        } else {
            return Console.ReadLine();
        }
    }
    
    public static int[] GetInt(char delimiter = ' ', bool mustTrim = false) {
        string src = ReadLine();
        if(mustTrim) {
            src = src.Trim();
        }
        string[] inpt = src.Split(delimiter);
        int[] ret = new int[inpt.Length];
        for(int i=0; i<inpt.Length; i++) {
            string item = inpt[i];
            if(mustTrim) {
                item = item.Trim();
            }
            ret[i] = int.Parse(item);
        }
        return ret;
    }
    
    private static string initStr = @"

2 5
01


";
}