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#include <iostream>
#include <iomanip>
#include <vector>
#include <array>
#include <set>

using namespace std;

//#define int long long

const long long INF = 1e9 + 7;
const int MAXN = 105;
const int N = 1e5 + 10;
const int MOD = 1e9 + 7;

int dp[MAXN][MAXN][MAXN];

void init_dp() {
    for (int i = 0; i < MAXN; ++i) {
        for (int j = 0; j < MAXN; ++j) {
            for (int k = 0; k < MAXN; ++k) {
                dp[i][j][k] = INF;
            }
        }
    }
}

signed main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    int n, m;
    cin >> n >> m;
    vector<int> a(n);
    for (int i = 0; i < n; ++i) {
        cin >> a[i];
    }
    init_dp();
    for (int i = 0; i < n; ++i) {
        for (int j = 1; j <= m; ++j) {
            dp[i][i][j] = (a[i] == j ? 0 : 1);
        }
    }
    for (int len = 2; len <= n; ++len) {
        for (int l = 0; l + len - 1 < n; ++l) {
            int r = l + len - 1;
            for (int col = 1; col <= m; ++col) {
                for (int mid = l; mid < r; ++mid) {
                    dp[l][r][col] = min(dp[l][r][col], dp[l][mid][col] + dp[mid + 1][r][col]);
                }
                if (a[l] == a[r]) {
                    if (len > 2) {
                        dp[l][r][col] = min(dp[l][r][col], dp[l + 1][r - 1][a[l]] + (a[l] == col ? 0 : 1));
                    } else {
                        dp[l][r][col] = min(dp[l][r][col], (a[l] == col ? 0 : 1));
                    }
                }
            }
        }
    }
    int ans = INF;
    for (int col = 1; col <= m; ++col) {
        ans = min(ans, dp[0][n - 1][col]);
    }
    cout << ans << '\n';
}