#include <iostream>
#include <algorithm>

using namespace std;

int N; //Number of ints

bool palindrome(int X[], int low, int high)
{
 if(high == low)
 return 1;

 int mid = (high - low)/2;
 for(int i = 0; i <= mid; i++)
 {
    if(X[low + i] != X[high - i])
    return 0;
 }
 return 1;
}



int main()
{
 ios::sync_with_stdio(0);

 cin >> N;

 int a[N];
 int bestpal[N + 1];

 for(int i = 0; i < N; i++){
 cin >> a[i];
 bestpal[i] = N + 1;
 }
 bestpal[N] = 0;

 for(int i = N - 1; i >= 0 ; i--)
 {
    for(int j = i; j < N; j++)
    {
    if(a[i] == a[j])
    {
    if(palindrome(a, i, j))
    bestpal[i] = min(1 + bestpal[j+1],bestpal[i]);
    }
    }

 }

 cout << bestpal[0];



}