/* FILE: collage-ric.cpp   last change: 8-Sept-2012   Romeo Rizzi
 * recursive solver for problem "collage" in 28-09-2012 exam in Algorithms
 */
#define NDEBUG   // NDEBUG definita nella versione che consegno
#include <cassert>
#ifndef NDEBUG
#  include <iostream>  // uso di cin e cout non consentito in versione finale
#endif
#include <fstream>
#include <cmath>

const int MAX_N = 1000;
int rainbow[MAX_N];
int n;

int memo[MAX_N][MAX_N];
const int UNKNOWN = -1;
//const int DROP = -1;
//const int LOOK = -2;


using namespace std;

int opt(int i, int j) {
	if (i>j) return 0;
	if (memo[i][j] == UNKNOWN) {
		memo[i][j] = 1 + opt(i+1, j);
		for (int sec = 1; i + sec <= j; ++sec) {
			if (rainbow[i+sec] == rainbow[i]) {
				memo[i][j] = min(memo[i][j], opt(i+1, i+sec-1) + opt(i+sec, j));
				// memo[i][j] = min(memo[i][j], opt(i, i+sec) + opt(i+sec, j) -1 );
			}
		}
	}
	return memo[i][j];
}



int main (int argc, char** argv) {
	ifstream in("input.txt"); assert(in);
	in >> n;
	for (int i = 0; i < n; ++i) {
		in >> rainbow[i];
	}
	in.close();
	//for (int i = 0; i < n; ++i)
	//	cout << rainbow[i] << " ";
	//cout << endl;
	
	for (int i = 0; i < n; ++i)
		for (int j = 0; j < n; ++j)
			memo[i][j] = UNKNOWN;
	
	ofstream out("output.txt"); assert(out);
	out << opt(0, n-1) << endl;
        out.close();
	
	return 0;
}