300 IQ abuse bitset

// clang-format off
#define _CRT_SECURE_NO_WARNINGS

#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <cmath>
#include <stack>
#include <iomanip>
#include <fstream>
#include <string>
#include <set>
#include <deque>
#include <queue>
#include <map>
#include <bitset>
#include <random>
#include <list>
#include <unordered_map>
#include <unordered_set>
#include <cassert>

using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef string str;
//typedef __int128 ultraint;
#define sqrt sqrtl
#define F first
#define S second
#define endl '\n'
#define all(vc666) vc666.begin(), vc666.end()
#define allr(vc666) vc666.rbegin(), vc666.rend()
//#define int long long
#define degug(x) cerr (#x) << " " << (x) << endl;

const ll INF = (ll)2e18 + 7;
const ll inf = 1e9 + 7;
const ll ONE = 1;
const ll MOD = 1e8;
ld EPS = 1e-12;
ld PI = 3.1415926535897932384;
mt19937_64 gen(3);
const ll max_sz = 405;

int dp[max_sz][max_sz];
bitset <max_sz> zxc[max_sz][max_sz];

void solve() {
    int n, M, i, j, l, r, m, sup, len;
    cin >> n >> M;
    for (i = 0; i < max_sz; i++) {
        for (j = 0; j < max_sz; j++) {
            dp[i][j] = inf;
        }
    }
    vector <int> a(n), cnt(M + 1);
    for (i = 0; i < n; i++) {
        cin >> a[i];
    }
    for (i = 0; i < n; i++) {
        dp[i][i] = 0;
        zxc[i][i][a[i]] = true;
    }
    for (len = 2; len <= n; len++) {
        for (l = 0; l <= n - len; l++) {
            r = l + len - 1;
            cnt.assign(M + 1, 0);
            for (i = l; i <= r; i++) {
                cnt[a[i]]++;
            }
            for (m = l; m < r; m++) {
                if (cnt[a[m]] > 1 && zxc[l][m][a[m]] && zxc[m + 1][r][a[m]]) {
                    if (dp[l][r] > dp[l][m] + dp[m + 1][r]) {
                        dp[l][r] = dp[l][m] + dp[m + 1][r];
                        zxc[l][r] = (zxc[l][m] & zxc[m + 1][r]);
                    }
                    else if (dp[l][r] == dp[l][m] + dp[m + 1][r]) {
                        zxc[l][r] |= (zxc[l][m] & zxc[m + 1][r]);
                    }
                }
                else {
                    if (dp[l][r] > dp[l][m] + dp[m + 1][r] + 1) {
                        dp[l][r] = dp[l][m] + dp[m + 1][r] + 1;
                        zxc[l][r] = (zxc[l][m] | zxc[m + 1][r]);
                    }
                    else if (dp[l][r] == dp[l][m] + dp[m + 1][r] + 1) {
                        zxc[l][r] |= (zxc[l][m] | zxc[m + 1][r]);
                    }
                }
                cnt[a[m]]--;
            }
        }
    }
    cout << dp[0][n - 1] << endl;
}

signed main() {
#ifdef _DEBUG
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif
    //freopen("ladder.in", "r", stdin);
    //freopen("ladder.out", "w", stdout);
    ios_base::sync_with_stdio(0);
    cin.tie(NULL);
    cout.tie(NULL);
    int t = 1;
    //cin >> t;
    while (t--) solve();
}
//Deisgned by skimono