content: package v117;
  
  
  import java.io.BufferedReader;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.InputStreamReader;
  import java.io.PrintWriter;
  import java.util.Arrays;
  import java.util.StringTokenizer;
  
  public class OptimalCut_UVa11782 {
  
  	static Scanner sc = new Scanner(System.in);
  	static PrintWriter out = new PrintWriter(System.out);
  	
  	static int[][] memo;
  	static int H, w[], level[];
  	
  	
  	static void build(int node, int lvl) throws IOException
  	{
  		w[node] = sc.nextInt();
  		level[node] = lvl;
  		if(lvl < H)
  		{
  			build(node<<1, lvl + 1);
  			build((node<<1) + 1, lvl + 1);
  		}
  	}
  	
  	static int dp(int node, int remK)
  	{
  		if(level[node] == H || remK == 1)
  			return w[node];
  		if(memo[node][remK] != -1)
  			return memo[node][remK];
  		int max = w[node];
  		for(int i = 1; i < remK; i++)
  			max = Math.max(max, dp(node<<1, i) + dp((node<<1) + 1, remK - i));
  		return memo[node][remK] = max;
  	}
  	
  	public static void main(String[] args) throws IOException {
  		
  		while(true)
  		{
  			H = sc.nextInt();
  			if(H == -1)
  				break;
  			int k = sc.nextInt();
  			w = new int[1<<H+1];
  			level = new int[1<<H+1];
  			build(1, 0);
  			memo = new int[1<<H+1][k + 1];
  			for(int i = 0; i < 1<<H+1; i++)
  				Arrays.fill(memo[i], -1);
  			out.println(dp(1, k));
  		}
  		out.flush();
  	}
  
  	static class Scanner 
  	{
  		StringTokenizer st;
  		BufferedReader br;
  
  		public Scanner(InputStream s){	br = new BufferedReader(new InputStreamReader(s));}
  
  		public String next() throws IOException 
  		{
  			while (st == null || !st.hasMoreTokens()) 
  				st = new StringTokenizer(br.readLine());
  			return st.nextToken();
  		}
  
  		public int nextInt() throws IOException {return Integer.parseInt(next());}
  		
  		public long nextLong() throws IOException {return Long.parseLong(next());}
  
  		public String nextLine() throws IOException {return br.readLine();}
  		
  		public double nextDouble() throws IOException
  		{
  			String x = next();
  			StringBuilder sb = new StringBuilder("0");
  			double res = 0, f = 1;
  			boolean dec = false, neg = false;
  			int start = 0;
  			if(x.charAt(0) == '-')
  			{
  				neg = true;
  				start++;
  			}
  			for(int i = start; i < x.length(); i++)
  				if(x.charAt(i) == '.')
  				{
  					res = Long.parseLong(sb.toString());
  					sb = new StringBuilder("0");
  					dec = true;
  				}
  				else
  				{
  					sb.append(x.charAt(i));
  					if(dec)
  						f *= 10;
  				}
  			res += Long.parseLong(sb.toString()) / f;
  			return res * (neg?-1:1);
  		}
  		
  		public boolean ready() throws IOException {return br.ready();}
  
  
  	}
  }
  