#include <bits/stdc++.h>
#define ll long long
#define mod 998244353
#define rep(i,s) for(ll i=0; i<s ; i++)
#define f(i,a,b) for(ll i(a); i<b ; i++)
#define inf -pow(10,9)
#define MAXN 100000
const ll INF = 1000000000;
const ll N = 3000;
const ll modi = 1000000007;
const ll modi2= 1000000006;
using namespace std;

int main(){
    ll n;
    cin >> n;
    ll arr[n];
    rep(i,n){
        cin >> arr[i];
    }
    ll dp[n][n];
    rep(i,n){
        rep(j,n){
            dp[i][j] = 1e18;
        }
    }
    vector<ll> v;
    v.push_back(arr[0]);
    f(i,1,n){
        if(arr[i] == arr[i-1]){
            continue;
        }
        v.push_back(arr[i]);
    }
    rep(i,v.size()){
        for(ll j = i; j>=0; j--){
            if(i==j){
                dp[i][j] = 1;
            }
            else{
                if(v[i] == v[j]){
                    dp[i][j] = min(dp[i-1][j], dp[i][j+1]);
                }
                else{
                    if(i - j == 1){
                        dp[i][j] = 2;
                        continue;
                    }
                    f(mid,j+1,i){
                        dp[i][j] = min(dp[i][j], dp[mid][j] + dp[i][mid + 1]);
                    }
                    dp[i][j] = min(dp[i][j], 1 + dp[i][j+1]);
                }
            }
        }
    }
    cout << dp[v.size()-1][0] << endl;
}