Problem: You are given a string s of length n consisting of lowercase Latin letters. You may apply some operations to this string: in one operation you can delete some contiguous substring of this string, if all letters in the substring you delete are equal. For example, after deleting substring bbbb from string abbbbaccdd we get the string aaccdd.

Calculate the minimum number of operations to delete the whole string s.

Input

The first line contains one integer n (1 ≤ n ≤ 500) — the length of string s.

The second line contains the string s (|s| = n) consisting of lowercase Latin letters.

Output

Output a single integer — the minimal number of operation to delete string s.

Examples

Input


5
abaca


Output


3

Input


8
abcddcba


Output


4

Solution (in JAVA):

Solution:
import java.io.*;
import java.util.*;
import java.math.*;
import java.math.BigInteger; 
//import javafx.util.*; 
public final class B
{    
	static PrintWriter out = new PrintWriter(System.out); 
	static StringBuilder ans=new StringBuilder();
	static FastReader in=new FastReader();
	static ArrayList<Integer> g[],og[];
	static long mod=(long)(1e9+7);
	static int D1[],D2[],par[];
	static boolean set[];
	static int value[];
	static long INF=Long.MAX_VALUE;
	static int N,M;
	static int val[],tot[],max[];
	static int min; //
	static int dp[][];
	public static void main(String args[])throws IOException
	{  					



		int N=i();
		dp=new int[N+1][N+1];
		for(int i=0; i<=N; i++)Arrays.fill(dp[i], -1);
		char A[]=in.next().toCharArray();
		out.println(f(0,N-1,A));
		out.close();

	}	
	static int f(int l,int r , char A[])
	{
		//System.out.println(l+" "+r);
		if(r<l)return 0;
		if(l==r)return dp[l][r]=1;
		if(dp[l][r]==-1)
		{
			if(dp[l+1][r]==-1)dp[l+1][r]=f(l+1,r,A);			
			dp[l][r]=1+dp[l+1][r];						
			for(int i=l+1; i<=r; i++)
			{
				if(A[l]==A[i])
				{
					dp[l][r]=Math.min(dp[l][r],f(l+1,i-1,A)+f(i,r,A));					
				}
			}
		}
		return dp[l][r];
	}
	static int f(int n,int p)
	{
		for(int c:g[n])
		{
			if(c!=p)val[n]+=f(c,n);
		}
		if(contains(p,og[n]))
			val[n]++;
		return val[n];
	}

	static boolean contains(int x,ArrayList<Integer>A)
	{
		int l=0,r=A.size()-1;
		while(l<=r)
		{
			int m=(l+r)/2;
			int a=A.get(m);
			if(a==x)return true;
			if(a<x)l=m+1;
			else r=m-1;
		}
		return false;
	}
	static boolean isPalin(char X[])
	{
		int l=0,r=X.length-1;
		while(l<=r)
		{
			if(X[l]!=X[r])return false;
			l++;
			r--;
		}
		return true;
	}

	static boolean isSorted(int A[])
	{
		int N=A.length;
		for(int i=0; i<N-1; i++)
		{
			if(A[i]>A[i+1])return false;
		}

		return true;		
	}
	static int f1(int x,ArrayList<Integer> A)
	{
		int l=-1,r=A.size();
		while(r-l>1)
		{
			int m=(l+r)/2;
			int a=A.get(m);
			if(a<x)l=m;
			else r=m;
		}		
		return l;
	}


	static int ask(int t,int i,int j,int x)
	{
		System.out.println("? "+t+" "+i+" "+j+" "+x);
		return i();
	}

	static int ask(int a)
	{
		System.out.println("? 1 "+a);
		return i();
	}
	static int f(int st,int end,int d)
	{
		if(st>end)return 0;
		int a=0,b=0,c=0;
		if(d>1)a=f(st+d-1,end,d-1);
		b=f(st+d,end,d);
		c=f(st+d+1,end,d+1);
		return value[st]+max(a,b,c);
	}
	static int max(int a,int b,int c)
	{
		return Math.max(a, Math.max(c, b));
	}
	static int value(char X[],char Y[])
	{
		int c=0;
		for(int i=0; i<7; i++)
		{
			if(Y[i]=='1' && X[i]=='0')return -1;
			if(X[i]=='1' && Y[i]=='0')c++;
		}
		return c;
	}
	static boolean isValid(int i,int j)
	{
		if(i<0 || i>=N)return false;
		if(j<0 || j>=M)return false;
		return true;
	}

	static long fact(long N)
	{
		long num=1L;
		while(N>=1)
		{
			num=((num%mod)*(N%mod))%mod;
			N--;
		}
		return num;
	}
	static boolean reverse(long A[],int l,int r)
	{
		while(l<r)
		{
			long t=A[l];
			A[l]=A[r];
			A[r]=t;
			l++;
			r--;
		}
		if(isSorted(A))return true;
		else return false;
	}
	static boolean isSorted(long A[])
	{
		for(int i=1; i<A.length; i++)if(A[i]<A[i-1])return false;
		return true;
	}
	static boolean isPalindrome(char X[],int l,int r)
	{
		while(l<r)
		{
			if(X[l]!=X[r])return false;
			l++; r--;
		}
		return true;
	}

	static long min(long a,long b,long c)
	{
		return Math.min(a, Math.min(c, b));
	}

	static void print(int a)
	{
		System.out.println("! "+a);
	}
	static int ask(int a,int b)
	{
		System.out.println("? "+a+" "+b);
		return i();
	}
	static int find(int a)
	{
		if(par[a]<0)return a;
		return par[a]=find(par[a]);
	}
	static void union(int a,int b)
	{
		a=find(a);
		b=find(b);
		if(a!=b)
		{
			par[a]+=par[b]; //transfers the size
			par[b]=a;       //changes the parent
		}
	}
	static void swap(char A[],int a,int b)
	{
		char ch=A[a];
		A[a]=A[b];
		A[b]=ch;
	}

	static void sort(long[] a) //check for long
	{
		ArrayList<Long> l=new ArrayList<>();
		for (long i:a) l.add(i);
		Collections.sort(l);
		for (int i=0; i<a.length; i++) a[i]=l.get(i);
	}
	static void setGraph(int N)
	{
		g=new ArrayList[N+1];		
		og=new ArrayList[N+1];

		val=new int[N+1];
		for(int i=0; i<=N; i++)
		{
			og[i]=new ArrayList<Integer>();			
			g[i]=new ArrayList<Integer>();
		}
	}

	static  long pow(long a,long b)
	{
		long mod=1000000007;
		long pow=1;
		long x=a;
		while(b!=0)
		{
			if((b&1)!=0)pow=(pow*x)%mod;
			x=(x*x)%mod;
			b/=2;
		}
		return pow;
	}
	static long toggleBits(long x)//one's complement || Toggle bits
	{
		int n=(int)(Math.floor(Math.log(x)/Math.log(2)))+1;

		return ((1<<n)-1)^x;
	}
	static int countBits(long a)
	{
		return (int)(Math.log(a)/Math.log(2)+1);
	}
	static void sort(int[] a) {
		ArrayList<Integer> l=new ArrayList<>();
		for (int i:a) l.add(i);
		Collections.sort(l);
		for (int i=0; i<a.length; i++) a[i]=l.get(i);
	}
	static boolean isPrime(long N)
	{
		if (N<=1)  return false; 
		if (N<=3)  return true; 
		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; 
	}
	static long GCD(long a,long b) 
	{
		if(b==0)
		{
			return a;
		}
		else return GCD(b,a%b );
	}

	//Debugging Functions Starts

	static void print(char A[])
	{
		for(char c:A)System.out.print(c+" ");
		System.out.println();
	}
	static void print(boolean A[])
	{
		for(boolean c:A)System.out.print(c+" ");
		System.out.println();
	}
	static void print(int A[])
	{
		for(int a:A)System.out.print(a+" ");
		System.out.println();	
	}
	static void print(long A[])
	{
		for(long i:A)System.out.print(i+ " ");
		System.out.println();

	}
	static void print(ArrayList<Integer> A)
	{
		for(int a:A)System.out.print(a+" ");
		System.out.println();
	}

	//Debugging Functions END
	//----------------------
	//IO FUNCTIONS STARTS
	static HashMap<Integer,Integer> Hash(int A[])
	{
		HashMap<Integer,Integer> mp=new HashMap<>();
		for(int a:A)
		{
			int f=mp.getOrDefault(a,0)+1;
			mp.put(a, f);
		}
		return mp;
	}
	static int i()
	{
		return in.nextInt();
	}

	static long l()
	{
		return in.nextLong();
	}

	static int[] input(int N){
		int A[]=new int[N];
		for(int i=0; i<N; i++)
		{
			A[i]=in.nextInt();
		}
		return A;
	}

	static long[] inputLong(int N)     {
		long A[]=new long[N];
		for(int i=0; i<A.length; i++)A[i]=in.nextLong();
		return A;
	}

	//IO FUNCTIONS END

}

class node implements Comparable<node>
{
	int x,index; boolean right;
	node(int x,boolean right,int index)
	{
		this.x=x;
		this.right=right;
		this.index=index;
	}
	public int compareTo(node X)
	{
		return this.x-X.x;
	}
}

//Code For FastReader
//Code For FastReader
//Code For FastReader
//Code For FastReader
class FastReader
{
	BufferedReader br;
	StringTokenizer st;
	public FastReader()
	{
		br=new BufferedReader(new InputStreamReader(System.in));
	}

	String next()
	{
		while(st==null || !st.hasMoreElements())
		{
			try
			{
				st=new StringTokenizer(br.readLine());
			}
			catch(IOException e)
			{
				e.printStackTrace();
			}
		}
		return st.nextToken();
	}

	int nextInt()
	{
		return Integer.parseInt(next());
	}

	long nextLong()
	{
		return Long.parseLong(next());
	}
	//gey
	double nextDouble()
	{
		return Double.parseDouble(next());
	}

	String nextLine()
	{
		String str="";
		try
		{
			str=br.readLine();
		}
		catch (IOException e)
		{
			e.printStackTrace();
		}
		return str;
	}

}