Nauuo is a girl who loves playing cards.

One day she was playing cards but found that the cards were mixed with some empty ones.

There are n cards numbered from 1 to n, and they were mixed with another n empty cards. She piled up the 2n cards and drew n of them. The n cards in Nauuo's hands are given. The remaining n cards in the pile are also given in the order from top to bottom.

In one operation she can choose a card in her hands and play it — put it at the bottom of the pile, then draw the top card from the pile.

Nauuo wants to make the n numbered cards piled up in increasing order (the i-th card in the pile from top to bottom is the card i) as quickly as possible. Can you tell her the minimum number of operations?

Input

The first line contains a single integer n (1≤ n≤ 2⋅ 10^5) — the number of numbered cards.

The second line contains n integers a_1,a_2,…,a_n (0≤ a_i≤ n) — the initial cards in Nauuo's hands. 0 represents an empty card.

The third line contains n integers b_1,b_2,…,b_n (0≤ b_i≤ n) — the initial cards in the pile, given in order from top to bottom. 0 represents an empty card.

It is guaranteed that each number from 1 to n appears exactly once, either in a_{1..n} or b_{1..n}.

Output

The output contains a single integer — the minimum number of operations to make the n numbered cards piled up in increasing order.

Examples

Input


3
0 2 0
3 0 1


Output


2

Input


3
0 2 0
1 0 3


Output


4

Input


11
0 0 0 5 0 0 0 4 0 0 11
9 2 6 0 8 1 7 0 3 0 10


Output


18

Note

Example 1

We can play the card 2 and draw the card 3 in the first operation. After that, we have [0,3,0] in hands and the cards in the pile are [0,1,2] from top to bottom.

Then, we play the card 3 in the second operation. The cards in the pile are [1,2,3], in which the cards are piled up in increasing order.

Example 2

Play an empty card and draw the card 1, then play 1, 2, 3 in order.
import java.io.BufferedWriter;
	import java.io.IOException;
	import java.io.InputStream;
	import java.io.OutputStream;
	import java.io.OutputStreamWriter;
	import java.io.PrintWriter;
	import java.io.Writer;
	import java.util.Arrays;
	import java.util.InputMismatchException;
	import java.util.*;
	import java.io.*;
	import java.math.*;
	public class Main7{

	static class Pair
		{ 
			int x; 
			int y;
			public Pair(int x, int y) 
			{	 
				this.x = x; 
				this.y = y;
			}	 
		} 
		static class Pair1
		{
			String x;
			int y;
			int z;
			
		}
		static class Compare
		{ 
			static void compare(Pair arr[], int n) 
			{ 
				// Comparator to sort the pair according to second element 
				Arrays.sort(arr, new Comparator<Pair>() { 
					@Override public int compare(Pair p1, Pair p2) 
					{ 
						if(p1.x>p2.x)
						{
							return 1;
						}
						else if(p1.x<p2.x)
						{
							return -1;
						}
						else
						{
							if(p1.y>p2.y)
							{
								return 1;
							}
							else
								return -1;
						}
					} 
				}); 
			} 
		}
		
		static class pqcomparator implements Comparator<Pair>
		{
		                // for Ascending order of cgpa 
            public int compare(Pair s1, Pair s2) { 
                if (s1.x > s2.x) 
                    return -1; 
                else if (s1.x < s2.x) 
                    return 1; 
                return 0; 
                } 
        } 
		
		
		public static long pow(long a, long b)
		{
			long result=1;
			while(b>0)
			{
				if (b % 2 != 0)
				{
					result=(result*a)%mod;
					b--;
				} 
				a=(a*a)%mod;
				b /= 2;
			}   
			return result;
		}
		public static long fact(long num)
		{
					long value=1;
					int i=0;
					for(i=2;i<num;i++)
					{
						value=((value%mod)*i%mod)%mod;
					}
					return value;
				}
				public static long gcd(long a, long b)
				{
					if (a == 0)
						return b;
					return gcd(b%a, a);
				}
				
				public static long lcm(long a,long b)
				{
					return a * (b / gcd(a, b));
				}
				public static long sum(int h)
				{
					return (h*(h+1)/2);
				}
				/*public static void dfs(int parent,boolean[] visited)
				{
					TreeSet<Integer> arr=new TreeSet<Integer>();
					arr=graph.get(parent);
					visited[parent]=true;
					if(a[parent]==1)
					{
						flag=1;
					}
					if(a[parent]==2)
					{
						flag1=1;
					}
					if(flag==1 && flag1==1)
					{
						return;
					}
					Iterator itr=arr.iterator();
					while(itr.hasNext())
					{
						int num=(int)itr.next();
						if(visited[num]==false)
						{
							dfs(num,visited);
						}
					}
					
				}*/
			//	static int flag1=0;
				static int[] dis;
				static long mod=64735492;
				static ArrayList<ArrayList<Integer>> graph;
				
				public static void bfs(int num,int size)
				{
					boolean[] visited=new boolean[size+1];
					Queue<Integer> q=new LinkedList<>();
					q.add(num);
					ans[num]=0;
					visited[num]=true;
					while(!q.isEmpty())
					{
						int x=q.poll();
						ArrayList<Integer> al=graph.get(x);
						for(int i=0;i<al.size();i++)
						{
							int y=al.get(i);	
							if(visited[y]==false)
							{
								q.add(y);
								visited[y]=true;
								ans[y]=ans[x]+1;
							}
							else
							{
								ans[y]=Math.min(ans[y],ans[x]+1);
							}
						}
						
					}
				}
				static int[] ans;
				
				
				
				
				
				
				
				
				
				
				
			//	static int[] a;			  
				
				public static long[] sort(long[] a)
				{
					int n=a.length;
					ArrayList<Long> ar=new ArrayList<>();
					for(int i=0;i<a.length;i++)
					{
						ar.add(a[i]);
					}
					Collections.sort(ar);
					for(int i=0;i<n;i++)
					{
						a[i]=ar.get(i);
					}
					return a;
				}
			//	static int flag=1;
		
			
			
			
			
			
			
			
			
			
			
			
			
			
			
			
			
			
			
			
			
			
			
				public static void main(String args[])throws IOException
				{
				//	InputReader in=new InputReader(System.in);
				//	OutputWriter out=new OutputWriter(System.out);
				//	long a=pow(26,1000000005);
				    BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
					ArrayList<Integer> ar4=new ArrayList<>();
					ArrayList<Integer> ar2=new ArrayList<>();
					
					ArrayList<Integer> ar1=new ArrayList<>();
			//		TreeSet<Integer> ts=new TreeSet<>();
			//		TreeSet<Long> ts1=new TreeSet<>();
				//	HashMap<Long,Integer> hash=new HashMap<>();
					HashMap<Integer,Integer> odd=new HashMap<Integer,Integer>();
					HashMap<Long,Integer> hash2=new HashMap<Long,Integer>();
				/*	boolean[] prime=new boolean[100001];
					for(int i=2;i*i<=100000;i++)
					{
						if(prime[i]==false)
						{
							for(int j=2*i;j<=100000;j+=i)
							{
								prime[j]=true;
							}
						}
					}*/
					int n=i();
					int[] a=new int[n];
					int[] flag=new int[n+1];
					for(int i=0;i<n;i++)
					{
						a[i]=i();
						flag[a[i]]=0;
					}
					int flag1=0;
					int index=-1;
					int[] b=new int[n];
					for(int i=0;i<n;i++)
					{
						b[i]=i();
						flag[b[i]]=i+1;
						if(b[i]==1)
						{
							flag1=1;
							index=i;
						}
					}
						
							int tmp=0;
							for(int i=index+1;i<n;i++)
							{
								if(b[i]==0)
								{
									tmp=1;
								}
								else if(b[i]!=i-index+1)
								{
									tmp=1;
								}
							}
					//		pln(index+" "+tmp);
							int ans=-1;
						//	pln(Arrays.toString(flag)+"");
							if(tmp==1)
							{
								int min=flag[1];
								ans=1;
								int j=1;
								for(int i=2;i<=n;i++)
								{
									if(flag[i]>min+j)
									{
										min=flag[i];
										ans=i;
										j=0;
									}
									j++;
								}
								int diff=0;
								if(ans>1)
									diff=min-flag[1]-(ans-1);
								pln(((flag[1]+diff)+n)+"");
							}
							else
							{
								if(index==n-1)
								{
									int min=flag[1]-1;
									int j=0;
									int ppo=0;
									for(int i=2;i<=n;i++)
									{
										if(flag[i]<=j)
										{
											
										}
										else
										{
											ppo=1;
										}
										j++;
									}
									if(ppo==0)
									{
										pln(index+"");
									}
									else
									{
										pln((flag[1]+n)+"");
									}
								}
								else
								{
									int num=(n-index);
									int ppo=0;
									int j=0;
									for(int i=num+1;i<=n;i++)
									{
										if(flag[i]<=j)
										{
											
										}
										else
										{
											ppo=1;
										}
										j++;
									}
									if(ppo==0)
									{
										pln(index+"");
									}
									else
									{
										pln((flag[1]+n)+"");
									}
								}
								
							}
						
					
				}
				
				
				
				
				/**/
				static InputReader in=new InputReader(System.in);
					static OutputWriter out=new OutputWriter(System.out);
					public static long l()
					{
						String s=in.String();
						return Long.parseLong(s);
					}
					public static void pln(String value)
					{
						System.out.println(value);
					}
					public static int i()
					{
						return in.Int();
					}
					public static String s()
					{
						return in.String();
					}
		}
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			class InputReader {
				 
				private InputStream stream;
				private byte[] buf = new byte[1024];
				private int curChar;
				private int numChars;
				private SpaceCharFilter filter;
			 
				public InputReader(InputStream stream) {
					this.stream = stream;
				}
			 
				public 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++];
				}
			 
				public int Int() {
					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;
				}
			 
				public String String() {
					int c = read();
					while (isSpaceChar(c))
						c = read();
					StringBuilder res = new StringBuilder();
					do {
						res.appendCodePoint(c);
						c = read();
					} while (!isSpaceChar(c));
					return res.toString();
				}
			 
				public boolean isSpaceChar(int c) {
					if (filter != null)
						return filter.isSpaceChar(c);
					return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
				}
			 
				public String next() {
					return String();
				}
			 
				public interface SpaceCharFilter {
					public boolean isSpaceChar(int ch);
				}
			}
			 
			class OutputWriter {
				private final PrintWriter writer;
			 
				public OutputWriter(OutputStream outputStream) {
					writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
				}
			 
				public OutputWriter(Writer writer) {
					this.writer = new PrintWriter(writer);
				}
			 
				public void print(Object...objects) {
					for (int i = 0; i < objects.length; i++) {
						if (i != 0)
							writer.print(' ');
						writer.print(objects[i]);
					}
				}
			 
				public void printLine(Object...objects) {
					print(objects);
					writer.println();
				}
			 
				public void close() {
					writer.close();
				}
			 
				public void flush() {
					writer.flush();
				}
			 
				}
			 
				class IOUtils {
			 
				public static int[] readIntArray(InputReader in, int size) {
					int[] array = new int[size];
					for (int i = 0; i < size; i++)
						array[i] = in.Int();
					return array;
				}
			 
				} 