#include <iostream>
#include <map>
#include <cstring>
#include <vector>
using ll=long long;

using namespace std;

int n;
int zuma[555];
int dp[555][555];

int rec(int i, int j) {
    if(i == j) {
        return 1;
    }
    if(i > j) {
        return 0;
    }
    if(dp[i][j] != -1) {
        return dp[i][j];
    }
    int result = 2e9;
    result = min(result, rec(i + 1, j) + 1);
    if(zuma[i] == zuma[i + 1]) {
        result = min(result, rec(i + 2, j) + 1);
    }

    for(int k = i + 2; k <= j; k++) {
        if(zuma[i] == zuma[k]) {
            result = min(result, rec(i + 1, k - 1) + rec(k + 1, j));
        }
    }

    return dp[i][j] = result;
}

int main()
{
    cin >> n;
    for(int i = 0; i < n; i++){
        cin >> zuma[i];
    }
    memset(dp, -1, sizeof dp);
    cout << rec(0, n - 1) << endl;
    return 0;
}