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.util.*;
import java.io.*;
import java.math.BigInteger;

/**
 *
 * @author usquare
 */

public class ProblemB{

    static long mod = (int) (1e9+7);
    static InputReader in;
    static PrintWriter out;
    static int n;
    static int maxn = 1000;
    static int[] arr;
    static int[][] dp;
    
    static void solve(){

        in = new InputReader(System.in);
        out = new PrintWriter(System.out);  
        
        n = in.nextInt();
        arr = in.nextIntArray(n);
        dp = new int[n + 2][n + 2];
        
        for(int i = 0; i < n; i++)
            for(int j = 0; j < n; j++)
                dp[i][j] = 0;
        
        for(int i = 0; i < n; i++)
            dp[i][i] = 1;
        
        for(int l = 2; l <= n; l++){
            for(int i = 0; i < n - 1; i++){
                int j = i + l - 1;
                if( j >= n)
                    continue;
                dp[i][j] = 1 + dp[i + 1][j];
                if(l == 2){
                    if(arr[i] == arr[j])
                        dp[i][j] = 1;
                }
                else{
                    if(arr[i] == arr[i + 1])
                        dp[i][j] = min(dp[i][j], 1 + dp[i + 2][j]);
                    for(int k = i + 2; k <= j; k++)
                        if(arr[i] == arr[k])
                            dp[i][j] = min(dp[i][j], dp[i + 1][k - 1] + dp[k + 1][j]);
                }   
            }
        }
        
        out.println(dp[0][n-1]);
        
        out.close();

    }
    
    public static void main(String[] args) {

        new Thread(null,new Runnable() {
            @Override
            public void run() {
                try{
                    solve();
                }
                catch(Exception e){
                    e.printStackTrace();
                }
            }
        },"1",1<<26).start();
    }

    static class Pair implements Comparable<Pair>{

        int x,y;
        long i;
        
	Pair (int x,int y,long i){
		this.x = x;
		this.y = y;
                this.i = i;
	}
        
        Pair (int x,int y){
		this.x = x;
		this.y = y;
	}
        
	public int compareTo(Pair o){
            if(this.i != o.i)
                    return Long.compare(this.i,o.i);
            if(this.x != o.x)
                    return Integer.compare(this.x,o.x);
            else
                    return Integer.compare(this.y,o.y);
		//return 0;
	}

        public boolean equals(Object o){
            if (o instanceof Pair) {
                Pair p = (Pair)o;
                return p.x == x && p.y==y;
            }
            return false;
        }

        @Override
        public String toString(){
            return x + " "+ y + " "+i;
        }
        
        public int hashCode(){
            return new Long(x).hashCode() * 31 + new Long(y).hashCode();
        }
    
    } 


    static class Merge{

        public static void sort(int inputArr[]){
            int length = inputArr.length;
            doMergeSort(inputArr,0, length - 1);
        }

        private static void doMergeSort(int[] arr,int lowerIndex, int higherIndex){        
            if (lowerIndex < higherIndex) {
                int middle = lowerIndex + (higherIndex - lowerIndex) / 2;
                doMergeSort(arr,lowerIndex, middle);
                doMergeSort(arr,middle + 1, higherIndex);
                mergeParts(arr,lowerIndex, middle, higherIndex);
            }
        }

        private static void mergeParts(int[]array,int lowerIndex, int middle, int higherIndex){
            int[] temp=new int[higherIndex-lowerIndex+1];
            for (int i = lowerIndex; i <= higherIndex; i++) {
                temp[i-lowerIndex] = array[i];
            }
            int i = lowerIndex;
            int j = middle + 1;
            int k = lowerIndex;
            while (i <= middle && j <= higherIndex) {
                if (temp[i-lowerIndex] < temp[j-lowerIndex]) {
                    array[k] = temp[i-lowerIndex];
                    i++;
                } else {
                    array[k] = temp[j-lowerIndex];
                    j++;
                }
                k++;
            }
            while (i <= middle) {
                array[k] = temp[i-lowerIndex];
                k++;
                i++;
            }
            while(j<=higherIndex){
                array[k]=temp[j-lowerIndex];
                k++;
                j++;
            }
        }

    }

    static long add(long a,long b){
        long x=(a+b);
        while(x>=mod) x-=mod;
        return x;
    }

    static long sub(long a,long b){
        long x=(a-b);
        while(x<0) x+=mod;
        return x;
    }

    static long mul(long a,long b){
        a%=mod;
        b%=mod;
        long x=(a*b);
        return x%mod;
    }


    static boolean isPal(String s){
        for(int i=0, j=s.length()-1;i<=j;i++,j--){
                if(s.charAt(i)!=s.charAt(j)) return false;
        }
        return true;
    }
    static String rev(String s){
                StringBuilder sb=new StringBuilder(s);
                sb.reverse();
                return sb.toString();
    }

    static long gcd(long x,long y){
        if(y==0)
                return x;
        else
                return gcd(y,x%y);
    }

    static int gcd(int x,int y){
        if(y==0)
                return x;
        else 
                return gcd(y,x%y);
    }

    static long gcdExtended(long a,long b,long[] x){

        if(a==0){
            x[0]=0;
            x[1]=1;
            return b;
        }
        long[] y=new long[2];
        long gcd=gcdExtended(b%a, a, y);

        x[0]=y[1]-(b/a)*y[0];
        x[1]=y[0];

        return gcd;
    }


    static long mulmod(long  a,long b,long m){
        if (m <= 1000000009) return a * b % m;

        long res = 0;
        while (a > 0) {
            if ((a&1)!=0) {
                res += b;
                if (res >= m) res -= m;
            }
            a >>= 1;
            b <<= 1;
            if (b >= m) b -= m;
        }
        return res;
    }

    static int abs(int a,int b){
        return (int)Math.abs(a-b);
    }

    public static long abs(long a,long b){
        return (long)Math.abs(a-b);
    }

    static int max(int a,int b){
        if(a>b)
                return a;
        else
                return b;
    }

    static int min(int a,int b){
        if(a>b)
                return b;
        else 
                return a;
    }

    static long max(long a,long b){
        if(a>b)
                return a;
        else
                return b;
    }

    static long min(long a,long b){
        if(a>b)
                return b;
        else 
                return a;
    }

    static long pow(long n,long p,long m){
         long  result = 1;
          if(p==0)
            return 1;

        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;
    }

    static long pow(long n,long p){
        long  result = 1;
          if(p==0)
            return 1;

        while(p!=0)
        {
            if(p%2==1)
                result *= n;	    
            p >>=1;
            n*=n;	    
        }
        return result;
    }

    static void debug(Object... o){
            System.out.println(Arrays.deepToString(o));
    }

    static class InputReader{

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

        public InputReader(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] = nextLong();
                }
                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);
        }

    }
}    
