Om Nom is the main character of a game "Cut the Rope". He is a bright little monster who likes visiting friends living at the other side of the park. However the dark old parks can scare even somebody as fearless as Om Nom, so he asks you to help him.

<image>

The park consists of 2n + 1 - 1 squares connected by roads so that the scheme of the park is a full binary tree of depth n. More formally, the entrance to the park is located at the square 1. The exits out of the park are located at squares 2n, 2n + 1, ..., 2n + 1 - 1 and these exits lead straight to the Om Nom friends' houses. From each square i (2 ≤ i < 2n + 1) there is a road to the square <image>. Thus, it is possible to go from the park entrance to each of the exits by walking along exactly n roads. 

<image> To light the path roads in the evening, the park keeper installed street lights along each road. The road that leads from square i to square <image> has ai lights.

Om Nom loves counting lights on the way to his friend. Om Nom is afraid of spiders who live in the park, so he doesn't like to walk along roads that are not enough lit. What he wants is that the way to any of his friends should have in total the same number of lights. That will make him feel safe. 

He asked you to help him install additional lights. Determine what minimum number of lights it is needed to additionally place on the park roads so that a path from the entrance to any exit of the park contains the same number of street lights. You may add an arbitrary number of street lights to each of the roads.

Input

The first line contains integer n (1 ≤ n ≤ 10) — the number of roads on the path from the entrance to any exit.

The next line contains 2n + 1 - 2 numbers a2, a3, ... a2n + 1 - 1 — the initial numbers of street lights on each road of the park. Here ai is the number of street lights on the road between squares i and <image>. All numbers ai are positive integers, not exceeding 100.

Output

Print the minimum number of street lights that we should add to the roads of the park to make Om Nom feel safe.

Examples

Input

2
1 2 3 4 5 6


Output

5

Note

Picture for the sample test. Green color denotes the additional street lights.

<image>
////package DFS;
import java.io.*;
import java.util.*;
/**
 *
 * @author prabhat
 */
public class P526B {

	static int[] a;
    static int[] S;
    static long[] sum;
   public static int mod=1000000007;
   static int[][] dp;
   static boolean[][] isPalin;
   static int max1=5000+10;
   static int[][] g;
   static int ver;
   static int n,m,k;
   static boolean[][] visit;
   static LinkedList<Pair> l[];
   static LinkedList<Integer> adj[];
   static boolean ans;
   static int[] color;
   static char[][] s;
   static int[] dx={1,0,-1,0};
   static int[] dy={0,-1,0,1};
   static int flag;
  public static void main(String[] args) throws Exception
   {
   	InputReader in = new InputReader(System.in);
   	PrintWriter pw=new PrintWriter(System.out);
         n=in.ii();
         a=new int[(1<<(n+1))];
        for(int i=0;i<((1<<(n+1))-2);i++)a[i+2]=in.ii();
        int ans=0;
        for(int i=(1<<n)-1;i>=1;i--)
        {
          int l=a[2*i];
          int r=a[2*i+1];
          ans+=Math.abs(l-r);
          a[i]+=Math.max(l,r);
        }
       // pw.println(Arrays.toString(a));
        pw.println(ans);
        
   	pw.close();
   }
 
  static class Lake implements Comparable<Lake> {
		int i, j, size;
		LinkedList<Pair> locs;

		Lake( int s, LinkedList<Pair> visitedLocs) {
			
			size = s;
			locs = visitedLocs;
		}

		@Override
		public int compareTo(Lake o) {
			return  size-o.size;
		}
	}

  static void dfs(int i,int j,int px,int py,LinkedList<Pair> l1)
  {
   if(i==0||i==n-1||j==0||j==m-1)
       flag=0;
      visit[i][j]=true;
      l1.add(new Pair(i,j));
	 for(int u=0;u<4;u++)
         {
           int nx=i+dx[u];
           int ny=j+dy[u];
           if((nx!=i||ny!=j)&&isValid(nx,ny)&&!visit[nx][ny]&&s[nx][ny]==s[i][j]&&s[nx][ny]=='.')
             {
                dfs(nx,ny,i,j,l1);
             }
          
         }
      
  }
  static boolean isValid(int i,int j)
  {
    if(i>=0&&i<=n-1&&j>=0&&j<=m-1)
        return true;
    return false;
  }
  private static class DSU{
		int[] parent;
		int[] rank;
		int cnt;
		public DSU(int n){
			parent=new int[n];
			rank=new int[n];
			for(int i=0;i<n;i++){
				parent[i]=i;
				rank[i]=1;
			}
			cnt=n;
		}
		int find(int i){
	        while(parent[i] !=i){
	        	parent[i]=parent[parent[i]];
	        	i=parent[i];
	        }
	        return i;
	    }
		int Union(int x, int y){
	        int xset = find(x);
	        int yset = find(y);
	        if(xset!=yset)
	        	cnt--;
	        if(rank[xset]<rank[yset]){
	        	parent[xset] = yset;
		        rank[yset]+=rank[xset];
		        rank[xset]=0;
		        return yset;
	        }else{
	        	parent[yset]=xset;
	        	rank[xset]+=rank[yset];
	        	rank[yset]=0;
	        	return xset;
	        }
	    }
	}
  public static int[][] packU(int n, int[] from, int[] to, int max) {
	    
	    int[][] g = new int[n][];
	    int[] p = new int[n];
	    for (int i = 0; i < max; i++) p[from[i]]++;
	    for (int i = 0; i < max; i++) p[to[i]]++;
	    for (int i = 0; i < n; i++) g[i] = new int[p[i]];
	    for (int i = 0; i < max; i++) {
	        g[from[i]][--p[from[i]]] = to[i];
	        g[to[i]][--p[to[i]]] = from[i];
	    }
	    return g;
	}
	public static int[][] parents3(int[][] g, int root) {
	    int n = g.length;
	    int[] par = new int[n];
	    Arrays.fill(par, -1);
 
	    int[] depth = new int[n];
	    depth[0] = 0;
 
	    int[] q = new int[n];
	    q[0] = root;
	    for (int p = 0, r = 1; p < r; p++) {
	        int cur = q[p];
	        for (int nex : g[cur]) {
	            if (par[cur] != nex) {
	                q[r++] = nex;
	                par[nex] = cur;
	                depth[nex] = depth[cur] + 1;
	            }
	        }
	    }
	    return new int[][]{par, q, depth};
	}
	public static int lower_bound(int[] nums, int target) {
        int low = 0, high = nums.length - 1;
        while (low < high) {
            int mid = low + (high - low) / 2;
            if (nums[mid] < target)
                low = mid + 1;
            else
                high = mid;
        }
        return nums[low] == target ? low : -1;
    }
 
    public static int upper_bound(int[] nums, int target) {
        int low = 0, high = nums.length - 1;
        while (low < high) {
            int mid = low + (high + 1 - low) / 2;
            if (nums[mid] > target)
                high = mid - 1;
            else
                low = mid;
        }
        return nums[low] == target ? low : -1;
    }
  public static boolean palin(String s)
	{
	   int i=0;
	   int j=s.length()-1;
	   while(i<j)
	   {
		   if(s.charAt(i)==s.charAt(j))
		   {
			   i++;
			   j--;
		   }
		   else return false;     
	   }
	   return true;
	}
	
    static boolean CountPs(String s,int n)
       {
    	boolean b=false;
    	     char[] S=s.toCharArray();
	       int[][] dp=new int[n][n];
	       boolean[][] p=new boolean[n][n];
	       for(int i=0;i<n;i++)p[i][i]=true;
	     
	       for(int i=0;i<n-1;i++)
	       {
	    	   if(S[i]==S[i+1])
	    	   {
	    		p[i][i+1]=true;
	    		dp[i][i+1]=1;
	    		b=true;
	    	   }
	       }
	    
	       for(int gap=2;gap<n;gap++)
	       {
	    	   for(int i=0;i<n-gap;i++)
	    	   {
	    		   int j=gap+i;
	    		   if(S[i]==S[j]&&p[i+1][j-1]){p[i][j]=true;}
	    		  
	    		  if(p[i][j])
	    			   dp[i][j]=dp[i][j-1]+dp[i+1][j]+1-dp[i+1][j-1];
	    		   
	    		   else  dp[i][j]=dp[i][j-1]+dp[i+1][j]-dp[i+1][j-1];
	    		  
	    		   if(dp[i][j]>=1){b=true;}
	    	   }
	       }
	      
	    return b; 
   // return dp[0][n-1];
	       
    }
  
  
  
 
 
public static int gcd(int a,int b)
{
	int res=1;
	while(a>0)
	{
		res=a;
		a=b%a;
		b=res;
	}
	return res;
}
 
 
public static long pow(long n,long p,long m)
{
	 long  result = 1;
	  if(p==0)
	    return 1;
	if (p==1)
	    return n;
	while(p!=0)
	{
	    if(p%2==1)
	        result *= n;
	    if(result>=m)
	    result%=m;
	    p >>=1;
	    n*=n;
	    if(n>=m)
	    n%=m;
	}
	return result;
}
public static long pow(long n,long p)
{
	long  result = 1;
	  if(p==0)
	    return 1;
	if (p==1)
	    return n;
	while(p!=0)
	{
	    if(p%2==1)
	        result *= n;
	    p >>=1;
	    n*=n;
	}
	return result;
 
}
 
 
 
 
static class Edge implements Comparator<Edge> {
	private int u;
	private int v;
	private int w;
	public Edge() {
	}
	public Edge(int u, int v, int w) {
		this.u=u;
		this.v=v;
		this.w=w;
	}
	public int getU() {
		return u;
	}
	public void setU(int u) {
		this.u = u;
	}
	public int getV() {
		return v;
	}
	public void setV(int v) {
		this.v = v;
	}
	public int getW() {
		return w;
	}
	public void setW(int w) {
		this.w = w;
	      }
	public int compareTo(Edge e)
	  {
		return this.getW() - e.getW();
	}
	@Override
	public String toString() {
		return "Edge [u=" + u + ", v=" + v + ", w=" + w + "]";
	}
	@Override
	public int compare(Edge arg0, Edge arg1) {
		// TODO Auto-generated method stub
		return 0;
	}
}
 
 
 
static class Pair implements Comparable<Pair>
{
	int a,b;
	Pair (int a,int b)
	{
		this.a=a;
		this.b=b;
	}
 
	public int compareTo(Pair o) {
		// TODO Auto-generated method stub
		if(this.a!=o.a)
		return -Integer.compare(this.a,o.a);
		else
			return -Integer.compare(this.b, o.b);
		//return 0;
	}
	public boolean equals(Object o) {
       if (o instanceof Pair) {
           Pair p = (Pair)o;
           return p.a == a && p.b == b;
       }
       return false;
   }
   public int hashCode() {
       return new Integer(a).hashCode() * 31 + new Integer(b).hashCode();
   }
}
 
static  class InputReader
{
   private InputStream stream;
   private byte[] buf = new byte[1024];
 
   private SpaceCharFilter filter;
    byte inbuffer[] = new byte[1024];
   int lenbuffer = 0, ptrbuffer = 0;
    final int M = (int) 1e9 + 7;
   int md=(int)(1e7+1);
    int[] SMP=new int[md];
   final double eps = 1e-6;
   final double pi = Math.PI;
 
	PrintWriter out;
   String check = "";
 InputStream   obj = check.isEmpty() ? System.in : new ByteArrayInputStream(check.getBytes());
   public InputReader(InputStream stream)
   {
       this.stream = stream;
   }
 
    int readByte() {
	        if (lenbuffer == -1) throw new InputMismatchException();
	        if (ptrbuffer >= lenbuffer) {
	            ptrbuffer = 0;
	            try {
	                lenbuffer = obj.read(inbuffer);
	            } catch (IOException e) {
	                throw new InputMismatchException();
	            }
	        }
	        if (lenbuffer <= 0) return -1;
	        return inbuffer[ptrbuffer++];
   }
 
   public  int read()
   {
       int c = read();
       while (isSpaceChar(c))
           c = read();
       int sgn = 1;
       if (c == '-')
       {
           sgn = -1;
           c = read();
       }
       int res = 0;
       do
       {
           if (c < '0' || c > '9')
               throw new InputMismatchException();
           res *= 10;
           res += c - '0';
           c = read();
       } while (!isSpaceChar(c));
       return res * sgn;
   }
 
   String is() {
	        int b = skip();
	        StringBuilder sb = new StringBuilder();
	        while (!(isSpaceChar(b))) // when nextLine, (isSpaceChar(b) && b!=' ')
	        {
	            sb.appendCodePoint(b);
	            b = readByte();
	        }
	        return sb.toString();
   }
   public   int ii() {
	        int num = 0, b;
	        boolean minus = false;
	        while ((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-')) ;
	        if (b == '-') {
	            minus = true;
	            b = readByte();
	        }
	        while (true) {
	            if (b >= '0' && b <= '9') {
	                num = num * 10 + (b - '0');
	            } else {
	                return minus ? -num : num;
	            }
	            b = readByte();
	        }
   }
 public   long il() {
	        long num = 0;
	        int b;
	        boolean minus = false;
	        while ((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-')) ;
	        if (b == '-') {
	            minus = true;
	            b = readByte();
	        }
	        while (true) {
	            if (b >= '0' && b <= '9') {
	                num = num * 10 + (b - '0');
	            } else {
	                return minus ? -num : num;
	            }
	            b = readByte();
	        }
   }
   
	    boolean isSpaceChar(int c) {
	        return (!(c >= 33 && c <= 126));
	       }
 
	      int skip()
	        {
	        int b;
	        while ((b = readByte()) != -1 && isSpaceChar(b)) ;
	        return b;
	        }
 
	    float nf() {
	        return Float.parseFloat(is());
	    }
 
	    double id() {
	        return Double.parseDouble(is());
	    }
 
	    char ic() {
	        return (char) skip();
	    }
 
	    int[] iia(int n) {
	        int a[] = new int[n];
	        for (int i = 0; i<n; i++) a[i] = ii();
	        return a;
	    }
 
	    long[] ila(int n) {
	        long a[] = new long[n];
	        for (int i = 0; i <n; i++) a[i] = il();
	        return a;
	    }
 
	    String[] isa(int n) {
	        String a[] = new String[n];
	        for (int i = 0; i < n; i++) a[i] = is();
	        return a;
	    }
 
 
		 long mul(long a, long b) { return a * b % M; }
 
			long div(long a, long b)
				 {
					return mul(a, pow(b, M - 2));
 
		           }
 
 
 
	    double[][] idm(int n, int m) {
	        double a[][] = new double[n][m];
	        for (int i = 0; i < n; i++) for (int j = 0; j < m; j++) a[i][j] = id();
	        return a;
	        }
 
	    int[][] iim(int n, int m) {
	        int a[][] = new int[n][m];
	        for (int i = 0; i < n; i++) for (int j = 0; j <m; j++) a[i][j] = ii();
	        return a;
          }
 
 
   public String readLine() {
       int c = read();
       while (isSpaceChar(c))
           c = read();
       StringBuilder res = new StringBuilder();
       do {
           res.appendCodePoint(c);
           c = read();
       } while (!isEndOfLine(c));
       return res.toString();
   }
 
   public interface SpaceCharFilter
   {
       public boolean isSpaceChar(int ch);
   }
   public boolean isEndOfLine(int c) {
       return c == '\n' || c == '\r' || c == -1;
   }
}
 
}
 