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>

	
	    /*
	     * Author- Priyam Vora
	     * BTech 2nd Year DAIICT
	     */
	     
	            
	    import java.io.*;
	    import java.math.*;
	    import java.util.*;
	    import javax.print.attribute.SetOfIntegerSyntax;
	     
	    public class Graph1 {
	    	private static InputStream stream;
	    	private static byte[] buf = new byte[1024];
	    	private static int curChar;
	    	private static int numChars;
	    	private static SpaceCharFilter filter;
	    	private static PrintWriter pw;
	    	private static long count = 0,mod=1000000007;
	    	private static TreeSet<Integer>ts[]=new TreeSet[200000];
	    	private static HashSet hs=new HashSet();
	     
	    	public static void main(String args[]) throws Exception {
	    		InputReader(System.in);
	    		pw = new PrintWriter(System.out);
	    		//ans();
	    		soln();
	    		pw.close();
	    	}
	     
	    	public static long gcd(long x, long y) {
	    		if (x == 0)
	    			return y;
	    		else
	    			return gcd( y % x,x);
	    	}
	    	
	    	private static int BinarySearch(int a[], int low, int high, int target) {
	    		if (low > high)
	    			return -1;
	    		int mid = low + (high - low) / 2;
	    		if (a[mid] == target)
	    			return mid;
	    		if (a[mid] > target)
	    			high = mid - 1;
	    		if (a[mid] < target)
	    			low = mid + 1;
	    		return BinarySearch(a, low, high, target);
	    	}
	    	
	    	public static String reverseString(String s) {
	    		StringBuilder sb = new StringBuilder(s);
	    		sb.reverse();
	    		return (sb.toString());
	    	}
	    	
	    	public static long pow(long n, long p) {
	    		if(p==0)
	    			return 1;
	    		if(p==1)
	    			return n%mod;
	    		if(p%2==0){
	    			long temp=pow(n, p/2);
	    		return (temp*temp)%mod;
	    		}else{
	    			 	long temp=pow(n,p/2);
	    			 	temp=(temp*temp)%mod;
	    			 	return(temp*n)%mod;
	    			 	
	    		}
	    	}
	     
	    		
	     
	    	public static int[] radixSort(int[] f) {
	    		int[] to = new int[f.length];
	    		{
	    			int[] b = new int[65537];
	    			for (int i = 0; i < f.length; i++)
	    				b[1 + (f[i] & 0xffff)]++;
	    			for (int i = 1; i <= 65536; i++)
	    				b[i] += b[i - 1];
	    			for (int i = 0; i < f.length; i++)
	    				to[b[f[i] & 0xffff]++] = f[i];
	    			int[] d = f;
	    			f = to;
	    			to = d;
	    		}
	    		{
	    			int[] b = new int[65537];
	    			for (int i = 0; i < f.length; i++)
	    				b[1 + (f[i] >>> 16)]++;
	    			for (int i = 1; i <= 65536; i++)
	    				b[i] += b[i - 1];
	    			for (int i = 0; i < f.length; i++)
	    				to[b[f[i] >>> 16]++] = f[i];
	    			int[] d = f;
	    			f = to;
	    			to = d;
	    		}
	    		return f;
	    	}
	     
	    	public static int nextPowerOf2(final int a) {
	    		int b = 1;
	    		while (b < a) {
	    			b = b << 1;
	    		}
	    		return b;
	    	}
	     
	    	public static boolean PointInTriangle(int p1, int p2, int p3, int p4, int p5, int p6, int p7, int p8) {
	    		int s = p2 * p5 - p1 * p6 + (p6 - p2) * p7 + (p1 - p5) * p8;
	    		int t = p1 * p4 - p2 * p3 + (p2 - p4) * p7 + (p3 - p1) * p8;
	     
	    		if ((s < 0) != (t < 0))
	    			return false;
	     
	    		int A = -p4 * p5 + p2 * (p5 - p3) + p1 * (p4 - p6) + p3 * p6;
	    		if (A < 0.0) {
	    			s = -s;
	    			t = -t;
	    			A = -A;
	    		}
	    		return s > 0 && t > 0 && (s + t) <= A;
	    	}
	     
	    	public static float area(int x1, int y1, int x2, int y2, int x3, int y3) {
	    		return (float) Math.abs((x1 * (y2 - y3) + x2 * (y3 - y1) + x3 * (y1 - y2)) / 2.0);
	    	}
	     
	    	public static boolean isPrime(int n) {
	    		// Corner cases
	    		if (n <= 1)
	    			return false;
	    		if (n <= 3)
	    			return true;
	     
	    		// This is checked so that we can skip 
	    		// middle five numbers in below loop
	    		if (n % 2 == 0 || n % 3 == 0)
	    			return false;
	     
	    		for (int i = 5; i * i <= n; i = i + 6)
	    			if (n % i == 0 || n % (i + 2) == 0)
	    				return false;
	     
	    		return true;
	    	}
	     
	    	//merge Sort
	     
	    	static long sort(int a[])
	    	{  int n=a.length;
	    		int b[]=new int[n];	
	    		return mergeSort(a,b,0,n-1);}
	    	static long mergeSort(int a[],int b[],long left,long right)
	    	{ long c=0;if(left<right)
	    	 {   long mid=left+(right-left)/2;
	    		 c= mergeSort(a,b,left,mid);
	    		 c+=mergeSort(a,b,mid+1,right);
	    		 c+=merge(a,b,left,mid+1,right); }	
	    		return c;	 }
	    	static long merge(int a[],int  b[],long left,long mid,long right)
	    	{long c=0;int i=(int)left;int j=(int)mid; int k=(int)left;
	    	while(i<=(int)mid-1&&j<=(int)right)
	    	{ if(a[i]>a[j]) {b[k++]=a[i++]; }
	    	else	{ b[k++]=a[j++];c+=mid-i;}}
	    	while (i <= (int)mid - 1)   b[k++] = a[i++]; 
	    	while (j <= (int)right) b[k++] = a[j++];
	    	for (i=(int)left; i <= (int)right; i++) 
	    		a[i] = b[i];  return c;  }
	    	public static boolean isSubSequence(String large, String small, int largeLen, int smallLen) {
	    		//base cases
	    		if (largeLen == 0)
	    			return false;
	    		if (smallLen == 0)
	    			return true;
	    		// If last characters of two strings are matching
	    		if (large.charAt(largeLen - 1) == small.charAt(smallLen - 1))
	    			isSubSequence(large, small, largeLen - 1, smallLen - 1);
	    		// If last characters are not matching
	    		return isSubSequence(large, small, largeLen - 1, smallLen);
	    	}
	     
	    	// To Get Input
	    	// Some Buffer Methods
	     
	    	public static void InputReader(InputStream stream1) {
	    		stream = stream1;
	    	}
	     
	    	private static boolean isWhitespace(int c) {
	    		return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
	    	}
	     
	    	private static boolean isEndOfLine(int c) {
	    		return c == '\n' || c == '\r' || c == -1;
	    	}
	     
	    	private static int read() {
	    		if (numChars == -1)
	    			throw new InputMismatchException();
	    		if (curChar >= numChars) {
	    			curChar = 0;
	    			try {
	    				numChars = stream.read(buf);
	    			} catch (IOException e) {
	    				throw new InputMismatchException();
	    			}
	    			if (numChars <= 0)
	    				return -1;
	    		}
	    		return buf[curChar++];
	    	}
	     
	    	private static int nextInt() {
	    		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;
	    	}
	     
	    	private static long nextLong() {
	    		int c = read();
	    		while (isSpaceChar(c))
	    			c = read();
	    		int sgn = 1;
	    		if (c == '-') {
	    			sgn = -1;
	    			c = read();
	    		}
	    		long res = 0;
	    		do {
	    			if (c < '0' || c > '9')
	    				throw new InputMismatchException();
	    			res *= 10;
	    			res += c - '0';
	    			c = read();
	    		} while (!isSpaceChar(c));
	    		return res * sgn;
	    	}
	     
	    	private static String nextToken() {
	    		int c = read();
	    		while (isSpaceChar(c))
	    			c = read();
	    		StringBuilder res = new StringBuilder();
	    		do {
	    			res.appendCodePoint(c);
	    			c = read();
	    		} while (!isSpaceChar(c));
	    		return res.toString();
	    	}
	     
	    	private static String nextLine() {
	    		int c = read();
	    		while (isSpaceChar(c))
	    			c = read();
	    		StringBuilder res = new StringBuilder();
	    		do {
	    			res.appendCodePoint(c);
	    			c = read();
	    		} while (!isEndOfLine(c));
	    		return res.toString();
	    	}
	     
	    	private static int[] nextIntArray(int n) {
	    		int[] arr = new int[n];
	    		for (int i = 0; i < n; i++) {
	    			arr[i] = nextInt();
	    		}
	    		return arr;
	    	}
	     
	    	private static int[][] next2dArray(int n, int m) {
	    		int[][] arr = new int[n][m];
	    		for (int i = 0; i < n; i++) {
	    			for (int j = 0; j < m; j++) {
	    				arr[i][j] = nextInt();
	    			}
	    		}
	    		return arr;
	    	}
	    	private static char[][] nextCharArray(int n,int m){
	    		char [][]c=new char[n][m];
	    		for(int i=0;i<n;i++){
	    			String s=nextLine();
	    			for(int j=0;j<s.length();j++){
	    				c[i][j]=s.charAt(j);
	    			}
	    		}
	    		return c;
	    	}
	     
	    	private static long[] nextLongArray(int n) {
	    		long[] arr = new long[n];
	    		for (int i = 0; i < n; i++) {
	    			arr[i] = nextLong();
	    		}
	    		return arr;
	    	}
	     
	    	private static void pArray(int[] arr) {
	    		for (int i = 0; i < arr.length; i++) {
	    			pw.print(arr[i] + " ");
	    		}
	    		pw.println();
	    		return;
	    	}
	     
	    	private static void pArray(long[] arr) {
	    		for (int i = 0; i < arr.length; i++) {
	    			pw.print(arr[i] + " ");
	    		}
	    		pw.println();
	    		return;
	    	}
	     
	    	private static void pArray(boolean[] arr) {
	    		for (int i = 0; i < arr.length; i++) {
	    			pw.print(arr[i] + " ");
	    		}
	    		pw.println();
	    		return;
	    	}
	     
	    	private static boolean isSpaceChar(int c) {
	    		if (filter != null)
	    			return filter.isSpaceChar(c);
	    		return isWhitespace(c);
	    	}
	     
	    	private interface SpaceCharFilter {
	    		public boolean isSpaceChar(int ch);
	    	}
	     
	    	static int col[];
	    	static boolean  vis[];
	    	//----------------------------------------My Code------------------------------------------------//
	    	private static void soln() {
	    		//-1 west 1 east 2 north -2 south
	    		int n=nextInt();
	
	    		int light[]=new int[(int)Math.pow(2, n+1)];
	    		for(int i=2;i<=Math.pow(2, n+1)-1;i++)
	    		{
	    			light[i]=nextInt();
	    		}
	    		 int ans=0;
	    		    for(int i=(int)Math.pow(2,n)-1;i>=1;i--)
	    		    {
	    		    	int left=light[2*i];
	    		    	int right=light[2*i+1];
	    		    	ans+=(2*Math.max(left, right))-left-right;
	    		    	light[i]+=Math.max(left, right);
	    		    }
	    		    System.out.println(ans);
	    		}
	    
	    	
	    	
	    	
	    		//-----------------------------------------The End--------------------------------------------------------------------------//
	    	
	    
	    
	    
	 }
	    	
	   
	    
		class Pair implements Comparable<Pair>{
		   
			int ind;
			int len;
			Pair(int ind,int len){
				this.ind=ind;
				this.len=len;
			}
			@Override
			public int compareTo(Pair o) {
				// TODO Auto-generated method stub
			//	Sort in increasing order
return 0;
			}
		
		}
	        class Graph{
	        	private static int V,level[][],count=-1,lev_dfs[],degree=0,no_vert_conn_comp=0;
	        	private Stack <Integer>st=new Stack();
	        	private static LinkedList<Integer > adj[];
	        	private boolean[][] Visite;
	        	private static boolean [] Visited;
	        	private static HashSet<Integer> Vis=new HashSet();
	        	private static Stack<Integer> topo_sort=new Stack<>();
	        	private static HashMap<Integer,Character> hm=new HashMap<>();
	        	private static ArrayList<Integer> col[];
	        	private static int color[];
		    
		    	
	    Graph(int V){
	    V++;
	    this.V=(V);
	    adj=new LinkedList[V];
	    Visite=new boolean[100][100];
	    
 	    Visited=new boolean[V];
	    level=new int[100][100];
	    lev_dfs=new int[V]; 
	   for(int i=0;i<V;i++)
		   adj[i]=new LinkedList<Integer>();
	
	    }
	    void setup(int n,int colo[]){
	    	color=new int[n+1];
	    	col=new ArrayList[100001];
	    	for(int i=1;i<=100000;i++){
	    		col[i]=new ArrayList<Integer>();
	    	}
	    	for(int i=1;i<=n;i++){
	    		col[colo[i]].add(i);
	    	}
	    	for(int i=1;i<=n;i++){
	    		color[i]=colo[i];
	    	}
	    }
	   void addEdge(int v,int w){
	    	
	    	if(adj[v]==null){
	    		adj[v]=new LinkedList();
	    	}
	    	adj[v].add(w);
	     
	    	
	    }
	  
	 public static void top_ans(){
	while(topo_sort.size()!=0)
{
	System.out.print(hm.get(topo_sort.peek()));
topo_sort.pop();
}
	
	 }
	 public static void topoSort(int startVert){
		 if(!Vis.contains(startVert)){
			 topoSortUtil(startVert);
		 }
	 }
	    public static void topoSortUtil(int curr_Vert){
	    	Vis.add(curr_Vert);
	    	Iterator<Integer> it=adj[curr_Vert].listIterator();
	    	
	    	while(it.hasNext()){
	    		int n=it.next();
	   // 		System.out.println(n);
	    		if(!Vis.contains(n)){
	    			topoSortUtil(n);
	    		}
	    		
	    	}
	    	topo_sort.push(curr_Vert);
	    }
	    
	    public static int BFS2(int startVert){
	    	Visited=new boolean[V];
	    	for(int i=1;i<V;i++){
	    		lev_dfs[i]=-1;
	    	}
	    	System.out.println(startVert);
	    	Queue<Integer> q=new LinkedList<Integer>();
	    	q.add(startVert);
	    	
	    	lev_dfs[startVert]=0;
	    	while(!q.isEmpty()){
	    		int top=q.poll();
	    		
	    		Iterator<Integer> i= adj[top].listIterator();
	    		while(i.hasNext()){
	    			int n=i.next();
	    			System.out.println(top+" "+n);
	    			if(!Visited[n]){
	    				q.add(n);
	    				Visited[n]=true;
	    				lev_dfs[n]=lev_dfs[top]+1;
	    			
	    			}
	    		}
	    	}
	    	for(int i=1;i<V;i++){
	    	System.out.println(lev_dfs[i]);
	    	}
	    //	q.clear();
	    	return -1;
	    }
	    public int getEd(){
	    	return degree/2;
	    }
	    public void get(int from,int to){
	    	int h=lev_dfs[from]-lev_dfs[to];
	    	if(h<=0){
	    		System.out.println(-1);
	    	}else{
	    		System.out.println(h-1);
	    	}
	    }
	    private static boolean check(int x,int y,char c[][]){
		
			if((x>=0 && y>=0) && (x<c.length && y<c[0].length) && c[x][y]!='#'){
				
				return true;
			}
			return false;
		}
	    public int BFS(int x,int y,int k,char[][] c)
	    {
	    	 LinkedList<Pair> queue = new LinkedList<Pair>();
	        //Visited[s]=true;
	   //     queue.add(new Pair(x,y));
	       int count=0;
	   level[x][y]=-1;
	   c[x][y]='M';
	        while (!queue.isEmpty())
	        {
	            Pair temp = queue.poll();
	            //x=temp.idx;
	            //y=temp.val;
	            
	            c[x][y]='M';
	      // System.out.println(x+" "+y+" ---"+count);
	         count++;
	     	if(count==k)
	         {
	         	for(int i=0;i<c.length;i++){
	         		for(int j=0;j<c[0].length;j++){
	         			if(c[i][j]=='M'){
	         				System.out.print(".");
	         			}
	         			else if(c[i][j]=='.')
	         				System.out.print("X");
	         			else
	         				System.out.print(c[i][j]);
	         		}
	         		System.out.println();
	         	}
	         System.exit(0);
	         }
	     	
	         // System.out.println(x+" "+y);
	           // V--;
	           
	        }
	        return V;
	    }
	    
	    public static void getAns(int n){
	    //ring
	    	int flag=1;
	    	int degree2=0;
	    	for(int i=1;i<V;i++){
	    		if(adj[i].size()==2){
	    		degree2++;
	    		}
	    	}
	    	 	if(degree2==(n)){
	    	 		System.out.println("ring topology");
	    	 	}else{
	    	 		int de_2=0,de_1=0;
	    	 		for(int i=1;i<V;i++){
	    	 			if(adj[i].size()==2){
	    	 				de_2++;
	    	 			}
	    	 			if(adj[i].size()==1)
	    	 				de_1++;
	    	 		}
	    	 		if(de_2==(n-2) && de_1==2){
	    	 			System.out.println("bus topology");
	    	 		}else{
	    	 			int deg_1=0,deg_n_1=0;
	    	 			for(int i=1;i<V;i++){
	    	 				if(adj[i].size()==1)
	    	 					deg_1++;
	    	 				if(adj[i].size()==(n-1))
	    	 					deg_n_1++;
	    	 			}
	    	 			if(deg_1==(n-1) && deg_n_1==1)
	    	 				System.out.println("star topology");
	    	 			else
	    	 				System.out.println("unknown topology");
	    	 		}
	    	 	}
	    	 	
	    }
	    
	     public long dfs(int startVertex,int[] col){
	    //	 getAns(startVertex);
	    	 
	    	 if(!Visited[startVertex])  {
	    
	   return dfsUtil(startVertex,col);
	    	//return getAns();
	    	}
	    	 
	    
	     
	    return 0;
	    	}
	 private long dfsUtil(int startVertex,int[] col) {//0-Blue 1-Pink
	//	 col_freq=new int[200001];
		// col_freq[col[startVertex-1]]++;
		 HashMap<Integer,Integer> hm=new HashMap<>();
		 int c=1;
		 hm.put(col[startVertex-1], 1);
		 long cout=0;
	      degree=0;
	    	Visited[startVertex]=true;
	    	lev_dfs[startVertex]=1;
	      st.push(startVertex);
	    while(!st.isEmpty()){
	    	
	    	int top=st.pop();
	    
	    //	ts.add(top);
	    	Iterator<Integer> i=adj[top].listIterator();
	     
	    while(i.hasNext()){
	    //	System.out.println(top);
	    	int n=i.next();
	     if( !Visited[n]){
	    				Visited[n]=true;
	    				
	    			//	col_freq[col[n-1]]++;
	    				c++;
	    				if(hm.containsKey(col[n-1])){
	    					hm.replace(col[n-1],hm.get(col[n-1])+1);
	    				}else{
	    					hm.put(col[n-1],1);
	    				}
	    				st.push(n);
	    					lev_dfs[n]=lev_dfs[top]+1;
	    			
	    		 }
	         }
	 }
	    int ans=0;
	  for(int x:hm.keySet()){
		  ans=Math.max(ans, hm.get(x));
	  }
	    
	    return c-ans;
	    	
	    		
	    
	  //  System.out.println("NO");
	   // return c;
	    	
	    
	    
	    
	    }
	        
	        }     
	       	        
	    class Dsu{
	    	private int rank[], parent[] ,n;
	    	
	    	Dsu(int size){
	    		this.n=size+1;
	    		rank=new int[n];
	    		parent=new int[n];
	    	makeSet();
	    	}
	    	
	    	void makeSet(){
	    		for(int i=0;i<n;i++){
	    			parent[i]=i;
	    		}
	    	}
	    	
	    	int find(int x){
	    		if(parent[x]!=x){
	    			
	    			parent[x]=find(parent[x]);
	    		}
	    		return parent[x];
	    	}	
	    	
	    	void union(int x,int y){
	    		int xRoot=find(x);
	    		int yRoot=find(y);
	    		
	    		if(xRoot==yRoot)
	    			return;
	    		if(rank[xRoot]<rank[yRoot]){
	    		parent[xRoot]=yRoot;	
	    		}else if(rank[yRoot]<rank[xRoot]){
	    			parent[yRoot]=xRoot;
	    		}else{
	    			parent[yRoot]=xRoot;
	    			rank[xRoot]++;
	    		}
	    		
	    	}
	     
	    }
	    class Heap{
	    	
	    	public static void build_max_heap(long []a,int size){
	    		
	    		for(int i=size/2;i>0;i--){
	    			max_heapify(a, i,size);
	    		}
	    		
	    			}
	    	private static void max_heapify(long[] a,int i,int size){
	    		int left_child=2*i;
	    		int right_child=(2*i+1);
	    		int largest=0;
	    		
	    		if(left_child<size && a[left_child]>a[i]){
	    			largest=left_child;
	    		}else{
	    			largest=i;
	    		}
	    		
	    		if(right_child<size && a[right_child]>a[largest]){
	    			largest=right_child;
	    		}
	    		if(largest!=i){
	    			long temp=a[largest];
	    			a[largest]=a[i];
	    			a[i]=temp;
	    			max_heapify(a, largest,size);
	    		}
	    	}
	    	private static void min_heapify(int[] a,int i){
	    		int left_child=2*i;
	    		int right_child=(2*i+1);
	    		int largest=0;
	    		
	    		if(left_child<a.length && a[left_child]<a[i]){
	    			largest=left_child;
	    		}else{
	    			largest=i;
	    		}
	    		
	    		if(right_child<a.length && a[right_child]<a[largest]){
	    			largest=right_child;
	    		}
	    		if(largest!=i){
	    			int temp=a[largest];
	    			a[largest]=a[i];
	    			a[i]=temp;
	    			min_heapify(a, largest);
	    		}
	    	}
	    	public static void extract_max(int size,long a[]){
	    		if(a.length>1){
	    			long max=a[1];
	    			a[1]=a[a.length-1];
	    			size--;
	    			max_heapify(a, 1,a.length-1);
	    		}
	    	}
	    }
	    
	    class MyComp implements Comparator<Long>{
	        
			@Override
			public int compare(Long o1, Long o2) {
				if(o1<o2){
					return 1;
				}else if(o1>o2){
					return -1;
				}
				return 0;
				
			}
	    }