#include<cstdio>
#include<algorithm>
#include<cstring>
#define MAXN 520
using namespace std;
int n;
int f[MAXN][MAXN],c[MAXN];
bool judge(int a,int b);
int main()
{
    memset(f,0x3f3f3f,sizeof(f));
    scanf("%d",&n);
    for(int i=1;i<=n;i++)
    {
        scanf("%d",&c[i]);
        f[i][i]
 
=1;
    }
    for(int len=1;len<=n;len++)
    {
        for(int i=1;i+len<=n;i++)
        {
            int j=i+len;
            if(judge(i,j))
            {
                printf("%d %d:HUIWEN\n",i,j);
                f[i][j]=1;
            }
            else
            {
                for
 
(int k=i;k<j;k++)
                {
                    f[i][j]=min(f[i][k]+f[k+1][j],f[i][j]);
                    printf("LEFT=%d|RIGHT=%d;k=%d____f[%d][%d]=%d\n",i,j,k,i,j,f[i][j]);
                }
            }
        }
    }
    printf("%d",f[1][n]);
    return 0;
}
bool judge(int a,int b)
{
    
 
if((b-a)==1)
    {
        if(c[a]==c[b]) return true;
        else return false;
    }
    int t=0;
    if((b-a)&1==0)
    {
        int temp=0;
        for(int i=a;i<=a+(b-a)/2;i++)
        {
            t=b-temp;
            temp++;
            if(c[i]!=c[t]) return false;
        }
    }
    else
    {
        int temp=0;
        for(int i=a;i<=a+(b-a+1)/2;i++)
        {
            t=b-temp;
            temp++;
            if(c[i]!=c[t]) return false;
        }
    }
    return true;
}