Genos recently installed the game Zuma on his phone. In Zuma there exists a line of n gemstones, the i-th of which has color ci. The goal of the game is to destroy all the gemstones in the line as quickly as possible.

In one second, Genos is able to choose exactly one continuous substring of colored gemstones that is a palindrome and remove it from the line. After the substring is removed, the remaining gemstones shift to form a solid line again. What is the minimum number of seconds needed to destroy the entire line?

Let us remind, that the string (or substring) is called palindrome, if it reads same backwards or forward. In our case this means the color of the first gemstone is equal to the color of the last one, the color of the second gemstone is equal to the color of the next to last and so on.

Input

The first line of input contains a single integer n (1 ≤ n ≤ 500) — the number of gemstones.

The second line contains n space-separated integers, the i-th of which is ci (1 ≤ ci ≤ n) — the color of the i-th gemstone in a line.

Output

Print a single integer — the minimum number of seconds needed to destroy the entire line.

Examples

Input

3
1 2 1


Output

1


Input

3
1 2 3


Output

3


Input

7
1 4 4 2 3 2 1


Output

2

Note

In the first sample, Genos can destroy the entire line in one second.

In the second sample, Genos can only destroy one gemstone at a time, so destroying three gemstones takes three seconds.

In the third sample, to achieve the optimal time of two seconds, destroy palindrome 4 4 first and then destroy palindrome 1 2 3 2 1.
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.ObjectInputStream.GetField;
import java.io.PrintWriter;
import java.math.BigDecimal;
import java.math.BigInteger;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.HashSet;
import java.util.InputMismatchException;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.PriorityQueue;
import java.util.Queue;
import java.util.Scanner;
import java.util.Stack;
import java.util.StringTokenizer;
import java.util.TreeMap;
import java.util.TreeSet;




	public class Q1 {
		
		static long MOD = 1000000007;
		static boolean b[], b1[], check;
		static ArrayList<Integer>[] amp, pa;
		static ArrayList<Pair>[] amp1;
		static ArrayList<Pair>[][] damp;
		static int left[],s[],right[],end[],sum[],dist[],cnt[],start[],color[],parent[],prime[],size[];
		static long ans = 0,k;
		static int p = 0;
		static FasterScanner sc = new FasterScanner(System.in);
		static Queue<Integer> q = new LinkedList<>();
		static PriorityQueue<Pair> pq;
		static BufferedWriter log;
		static HashSet<Integer>[] hs;
		static HashMap<Pair,Integer> hm;
		static Stack<Integer> st;
		static boolean boo[][];
		static Pair prr[];
		static long parent1[],parent2[],size1[],size2[],arr1[],SUM[],MAX[];
		static int arr[];
		public static void main(String[] args) throws Exception {
	    	/*new Thread(null, new Runnable() {
				public void run() {
					try {

				} catch (Exception e) {
						System.out.println(e);
					}
				}
			}, "1", 1 << 26).start();*/
			soln();
		}
		static int dp[][];
		static int N,K,T;
		static int time;
		static int cost[][];
		static boolean b11[];
		static HashMap<Integer,Integer> h = new HashMap<>();
		static long ans1;
		static long ans2;
		static int BLOCK = 350;
		public static void soln() throws IOException {
			//FasterScanner in = new FasterScanner(new FileInputStream("C:\\Users\\Admin\\Desktop\\QCS1.txt"));
			//PrintWriter out = new PrintWriter("C:\\Users\\Admin\\Desktop\\A1.txt");
			log = new BufferedWriter(new OutputStreamWriter(System.out));
			int n = sc.nextInt();
			N = n;
			arr = sc.nextIntArray(n);
			dp = new int[n][n];
			for(int i = 0; i< n; i++) Arrays.fill(dp[i], Integer.MAX_VALUE/2);
			System.out.println(recur(0,n-1));
			log.close();
			//out.close();
		}
		static int recur(int l, int r){
			if(l<0 || r<0 || l>N || r>N) return Integer.MAX_VALUE/2;
			if(l>r) return 1;
			if(l==r) return 1;
			if(dp[l][r]!=Integer.MAX_VALUE/2) return dp[l][r];
			if(arr[l]==arr[r]){
				dp[l][r] = Math.min(dp[l][r], recur(l+1,r-1));
			}
			for(int i = l; i< r; i++){
				dp[l][r] = Math.min(dp[l][r], recur(l,i)+recur(i+1,r));	
			}
			return dp[l][r];
		}
		static void bfs(int x){
			
		}
		static void dfs(int x){
			b[x] = true;
			if(amp[x].size()%2==1) p++;
			for(int p:amp[x]){
				if(!b[p]){
					dfs(p);
				}
			}
		}
		public static void seive(int n){
			b = new boolean[(n+1)];
			Arrays.fill(b, true);
			b[1] = false;
			for(int i = 2;i*i<=n;i++){
				if(b[i]){
					for(int p = 2*i;p<=n;p+=i){
						b[p] = false;
					}
				}
			}
			/*for(int i = 2;i<=n;i++){
				if(b[i]) prime[i] = i;
			}*/
		}
		
		static class Graph{
			int vertex;
			int weight;
			Graph(int v, int w){
				vertex = v;
				weight = w;
			}
		}
		static class Pair implements Comparable<Pair> {
			long u;
			int v;
			public Pair(){
				u = 0;
				v = 0;
			}
			public Pair(long u, int v) {
				this.u = u;
				this.v = v;
			}
			public int hashCode() {
				int hu = (int) (u ^ (u >>> 32));
				int hv = (int) (v ^ (v >>> 32));
				return 31*hu + hv;
			}
	 
			public boolean equals(Object o) {
				Pair other = (Pair) o;
				return (u == other.u && v == other.v);
			}
	 
			public int compareTo(Pair other) {
				return Long.compare(u, other.u) != 0 ? (Long.compare(u, other.u)) : (Long.compare(v,other.v));
			}
			
			public String toString() {
				return "[u=" + u + ", v=" + v + "]";
			}
		}
		
		public static void buildGraph(int n){
			for(int i =0;i<n;i++){
				int x = sc.nextInt()-1, y = sc.nextInt()-1;
				hm.put(new Pair(x,y), i+1);
				amp[x].add(y);
				amp[y].add(x);
			}
		}
		
		
		public static int getParent(long x){
			while(parent[(int) x]!=x){
				parent[ (int) x] = parent[(int) parent[ (int) x]];
				x = parent[ (int) x];
			}
			return (int) x;
		}
		static long min(long a, long b, long c){
			if(a<b && a<c) return a;
			if(b<c) return b;
			return c;
		}
		/*
		
		static class Pair3{
			int x, y ,z;
			Pair3(int x, int y, int z){
				this.x = x;
				this.y = y;
				this.z = z;
			}
		}*/
		static int sum(int n){
			String str = Integer.toString(n);
			int cnt = 0;
			for(int i = 0; i< str.length();i++){
				cnt+=(str.charAt(i)-'0');
			}
			return cnt;
		}
		 static void KMPSearch(String pat, String txt)
		    {
		        int M = pat.length();
		        int N = txt.length();
		 
		        // create lps[] that will hold the longest
		        // prefix suffix values for pattern
		        int lps[] = new int[M];
		        int j = 0;  // index for pat[]
		 
		        // Preprocess the pattern (calculate lps[]
		        // array)
		        computeLPSArray(pat,M,lps);
		 
		        int i = 0;  // index for txt[]
		        while (i < N)
		        {
		            if (pat.charAt(j) == txt.charAt(i))
		            {
		                j++;
		                i++;
		            }
		            if (j == M)
		            {
		               // parent.add((i-j));
		                j = lps[j-1];
		            }
		 
		            // mismatch after j matches
		            else if (i < N && pat.charAt(j) != txt.charAt(i))
		            {
		                // Do not match lps[0..lps[j-1]] characters,
		                // they will match anyway
		                if (j != 0)
		                    j = lps[j-1];
		                else
		                    i = i+1;
		            }
		        }
		    }
		 static void computeLPSArray(String pat, int M, int lps[])
		    {
		        // length of the previous longest prefix suffix
		        int len = 0;
		        int i = 1;
		        lps[0] = 0;  // lps[0] is always 0
		 
		        // the loop calculates lps[i] for i = 1 to M-1
		        while (i < M)
		        {
		            if (pat.charAt(i) == pat.charAt(len))
		            {
		                len++;
		                lps[i] = len;
		                i++;
		            }
		            else  // (pat[i] != pat[len])
		            {
		                // This is tricky. Consider the example.
		                // AAACAAAA and i = 7. The idea is similar 
		                // to search step.
		                if (len != 0)
		                {
		                    len = lps[len-1];
		 
		                    // Also, note that we do not increment
		                    // i here
		                }
		                else  // if (len == 0)
		                {
		                    lps[i] = len;
		                    i++;
		                }
		            }
		        }
		    }
		private static void permutation(String prefix, String str) {
		    int n = str.length();
		    if (n == 0); //hs.add(prefix);
		    else {
		        for (int i = 0; i < n; i++)
		            permutation(prefix + str.charAt(i), str.substring(0, i) + str.substring(i+1, n));
		    }
		}
		public static char give(char c1,char c2){
			if(c1!='a' && c2!='a') return 'a';
			if(c1!='b' && c2!='b') return 'b';
			return 'c';
		}
		
		public static void buildTree(int n){
			int arr[] = sc.nextIntArray(n);
			for(int i = 0;i<n;i++){
				int x = arr[i]-1;
				amp[i+1].add(x);
				amp[x].add(i+1);
			}
		}
		
		static class SegmentTree {
			boolean st[];
			boolean lazy[];

			SegmentTree(int n) {
				int size = 4 * n;
				st = new boolean[size];
				Arrays.fill(st, true);
				lazy = new boolean[size];
				Arrays.fill(lazy, true);
				//build(0, n - 1, 1);
			}
			
			/*long[] build(int ss, int se, int si) {
				if (ss == se) {
					st[si][0] = 1;
					st[si][1] = 1;
					st[si][2] = 1;
					return st[si];
				}
				int mid = (ss + se) / 2;
				long a1[] = build(ss, mid, si * 2), a2[] = build(mid + 1, se,
						si * 2 + 1);
				long ans[] = new long[3];
				if (arr[mid] < arr[mid + 1]) {
					ans[1] = Math.max(a2[1], Math.max(a1[1], a1[2] + a2[0]));
					if (a1[1] == (mid - ss + 1))
						ans[0] = ans[1];
					else
						ans[0] = a1[0];
					if (a2[2] == (se - mid))
						ans[2] = ans[1];
					else
						ans[2] = a2[2];
				} else {
					ans[1] = Math.max(a1[1], a2[1]);
					ans[0] = a1[0];
					ans[2] = a2[2];
				}
				st[si] = ans;
				return st[si];
			}*/

			void update(int si, int ss, int se, int idx, long x) {
				if (ss == se) {
					//arr[idx] += val;
					st[si]=false;
				} 
				else {
					int mid = (ss + se) / 2;
					if(ss <= idx && idx <= mid)
			        {
			             update(2*si, ss, mid, idx, x);
			        }
			        else
			        { update(2*si+1, mid+1, se, idx, x);
			        }
					st[si] = st[2*si]|st[2*si+1];
				}
			}
			/*boolean get(int qs, int qe, int ss, int se, int si){
				if(qs>se || qe<ss) return 0;
				if (qs <= ss && qe >= se) {
					return st[si];
				}
				int mid = (ss+se)/2;
				return get(qs, qe, ss, mid, si * 2)+get(qs, qe, mid + 1, se, si * 2 + 1);
			}*/
			void updateRange(int node, int start, int end, int l, int r, boolean val)
			{
			    if(!lazy[node])
			    { 
			        // This node needs to be updated
			        st[node] = lazy[node];    // Update it
			        if(start != end)
			        {
			            lazy[node*2] = lazy[node];                  // Mark child as lazy
			            lazy[node*2+1] = lazy[node];                // Mark child as lazy
			        }
			        lazy[node] = true;                                  // Reset it
			    }
			    if(start > end || start > r || end < l)              // Current segment is not within range [l, r]
			        return;
			    if(start >= l && end <= r)
			    {
			        // Segment is fully within range
			        st[node] =  val;
			        if(start != end)
			        {
			            // Not leaf node
			            lazy[node*2] = val;
			            lazy[node*2+1] = val;
			        }
			        return;
			    }
			    int mid = (start + end) / 2;
			    updateRange(node*2, start, mid, l, r, val);        // Updating left child
			    updateRange(node*2 + 1, mid + 1, end, l, r, val);   // Updating right child
			    st[node] = st[node*2] | st[node*2+1];        // Updating root with max value 
			}

			boolean queryRange(int node, int start, int end, int l, int r)
			{
			    if(start > end || start > r || end < l)
			        return false;         // Out of range
			    if(!lazy[node])
			    {
			        // This node needs to be updated
			        st[node] = lazy[node];            // Update it
			        if(start != end)
			        {
			            lazy[node*2] = lazy[node];         // Mark child as lazy
			            lazy[node*2+1] = lazy[node];    // Mark child as lazy
			        }
			        lazy[node] = true;                 // Reset it
			    }
			    if(start >= l && end <= r)             // Current segment is totally within range [l, r]
			        return  st[node];
			    int mid = (start + end) / 2;
			    boolean p1 = queryRange(node*2, start, mid, l, r);         // Query left child
			    boolean b = queryRange(node*2 + 1, mid + 1, end, l, r); // Query right child
			    return (p1 | b);
			}
			void print() {
				for (int i = 0; i < st.length; i++) {
					System.out.print(st[i]+" ");
				}
				System.out.println();
			}
		}
		static int convert(int x){
			int cnt = 0;
			String str = Integer.toBinaryString(x);
			//System.out.println(str);
			for(int i = 0;i<str.length();i++){
				if(str.charAt(i)=='1'){
					cnt++;
				}
			}
			int ans = (int) Math.pow(3, 6-cnt);
			return ans;
		}
		static class Node2{
			Node2 left = null;
			Node2 right = null;
			Node2 parent = null;
			int data;
		}
		static class BinarySearchTree{
			Node2 root = null;
			int height = 0;
			int max = 0;
			int cnt = 1;
			ArrayList<Integer> parent = new ArrayList<>();
			HashMap<Integer, Integer> hm = new HashMap<>();
			public void insert(int x){
				Node2 n = new Node2();
				n.data = x;
				if(root==null){
					root = n;
				}
				else{
					Node2 temp = root,temb = null;
					while(temp!=null){
						temb = temp;
						if(x>temp.data) temp = temp.right;
						else temp = temp.left;
					}
					if(x>temb.data) temb.right = n;
					else temb.left = n;
					n.parent = temb;
					parent.add(temb.data);
				}
			}
			public Node2 getSomething(int x, int y, Node2 n){
				if(n.data==x || n.data==y) return n;
				else if(n.data>x && n.data<y) return n;
				else if(n.data<x && n.data<y) return getSomething(x,y,n.right);
				else return getSomething(x,y,n.left);
			}
			public Node2 search(int x,Node2 n){
				if(x==n.data){
					max = Math.max(max, n.data);
					return n;
				}
				if(x>n.data){
					max = Math.max(max, n.data);
					return search(x,n.right);
				}
				else{
					max = Math.max(max, n.data);
					return search(x,n.left);
				}
			}
			public int getHeight(Node2 n){
				if(n==null) return 0;
				height = 1+ Math.max(getHeight(n.left), getHeight(n.right));
				return height;
			}
		}
		static long findDiff(long[] arr, long[] brr, int m){
			int i = 0, j = 0;
			long fa = 1000000000000L;
			while(i<m && j<m){
				long x = arr[i]-brr[j];
				if(x>=0){
					if(x<fa) fa = x;
					j++;
				}
				else{
					if((-x)<fa) fa = -x;
					i++;
				}
			}
			return fa;
		}
		public static long max(long x, long y, long z){
			if(x>=y && x>=z) return x;
			if(y>=x && y>=z) return y;
			return z;
		}
		
		static long modInverse(long a, long mOD2){
		            return  power(a, mOD2-2, mOD2);
		}
		static long power(long x, long y, long m)
		{
		    if (y == 0)
		        return 1;
		    long p = power(x, y/2, m) % m;
		    p = (p * p) % m;
		 
		    return (y%2 == 0)? p : (x * p) % m;
		}
		static long power2(long x,BigInteger y,long m){
			long ans = 1;
			BigInteger two = new BigInteger("2");
			while(y.compareTo(BigInteger.ZERO)>0){
				if(y.getLowestSetBit()==y.bitCount()){
					x = (x*x)%MOD;
					y = y.divide(two);
				}
				else{
					ans = (ans*x)%MOD;
					y = y.subtract(BigInteger.ONE);
				}
			}
			return ans;
		}
		static BigInteger power2(BigInteger x, BigInteger y, BigInteger m){
			BigInteger ans = new BigInteger("1");
			BigInteger one  = new BigInteger("1");
			BigInteger two  = new BigInteger("2");
			BigInteger zero  = new BigInteger("0");
			while(y.compareTo(zero)>0){
				//System.out.println(y);
				if(y.mod(two).equals(one)){
					ans = ans.multiply(x).mod(m);
					y = y.subtract(one);
				}
				else{
					x = x.multiply(x).mod(m);
					y = y.divide(two);
				}
			}
			return ans;
		}
		static BigInteger power(BigInteger x, BigInteger y, BigInteger m)
		{
		    if (y.equals(0))
		        return (new BigInteger("1"));
		    BigInteger p = power(x, y.divide(new BigInteger("2")), m).mod(m);
		    p = (p.multiply(p)).mod(m);
		 
		    return (y.mod(new BigInteger("2")).equals(0))? p : (p.multiply(x)).mod(m);
		}
		static long d,x,y;
		public static void extendedEuclidian(long a, long b){
			if(b == 0) {
		        d = a;
		        x = 1;
		        y = 0;
		    }
		    else {
		        extendedEuclidian(b, a%b);
		        int temp = (int) x;
		        x = y;
		        y = temp - (a/b)*y;
		    }
		}
		
		public static long gcd(long n, long m){
			if(m!=0) return gcd(m,n%m);
			else return n;
		}
		
		static BufferedReader reader;
	    static StringTokenizer tokenizer;
	    static PrintWriter writer;
	
	
	   
	    static class FasterScanner {

			private final InputStream stream;
			private final byte[] buf = new byte[8192];
			private int curChar, snumChars;
			private SpaceCharFilter filter;

			public FasterScanner(InputStream stream) {
				this.stream = stream;
			}

			public int snext() {
				if (snumChars == -1)
					throw new InputMismatchException();
				if (curChar >= snumChars) {
					curChar = 0;
					try {
						snumChars = stream.read(buf);
					} catch (IOException e) {
						throw new InputMismatchException();
					}
					if (snumChars <= 0)
						return -1;
				}
				return buf[curChar++];
			}

			public int nextInt() {
				int c = snext();
				while (isSpaceChar(c)) {
					c = snext();
				}
				int sgn = 1;
				if (c == '-') {
					sgn = -1;
					c = snext();
				}
				int res = 0;
				do {
					if (c < '0' || c > '9')
						throw new InputMismatchException();
					res *= 10;
					res += c - '0';
					c = snext();
				} while (!isSpaceChar(c));
				return res * sgn;
			}

			public long nextLong() {
				int c = snext();
				while (isSpaceChar(c)) {
					c = snext();
				}
				int sgn = 1;
				if (c == '-') {
					sgn = -1;
					c = snext();
				}
				long res = 0;
				do {
					if (c < '0' || c > '9')
						throw new InputMismatchException();
					res *= 10;
					res += c - '0';
					c = snext();
				} while (!isSpaceChar(c));
				return res * sgn;
			}

			public int[] nextIntArray(int n) {
				int a[] = new int[n];
				for (int i = 0; i < n; i++) {
					a[i] = nextInt();
				}
				return a;
			}

			public long[] nextLongArray(int n) {
				long a[] = new long[n];
				for (int i = 0; i < n; i++) {
					a[i] = nextInt();
				}
				return a;
			}
	                
			public String readString() {
				int c = snext();
				while (isSpaceChar(c)) {
					c = snext();
				}
				StringBuilder res = new StringBuilder();
				do {
					res.appendCodePoint(c);
					c = snext();
				} while (!isSpaceChar(c));
				return res.toString();
			}

			public String nextLine() {
				int c = snext();
				while (isSpaceChar(c))
					c = snext();
				StringBuilder res = new StringBuilder();
				do {
					res.appendCodePoint(c);
					c = snext();
				} while (!isEndOfLine(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;
			}

			private boolean isEndOfLine(int c) {
				return c == '\n' || c == '\r' || c == -1;
			}

			public interface SpaceCharFilter {
				public boolean isSpaceChar(int ch);
			}
		}
	}  