import java.util.*;
public class rangeediting_xiaowuc1 {
  public static void main(String[] args) throws Exception {
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int[] l = new int[n+2];
    for(int i = 1; i <= n; i++) l[i] = sc.nextInt();
    int[][] dp = new int[n+3][n+3];
    for(int len = 2; len <= n+2; len++) {
      Arrays.fill(dp[len], 1 << 25);
      for(int smalllen = 1; smalllen < len; smalllen++) {
        for(int i = 0; i + len <= n+2; i++) {
          dp[len][i] = Math.min(
            dp[len][i],
            dp[smalllen][i] + dp[len-smalllen][i+smalllen] + (l[i] != l[i+smalllen] ? 1 : 0)
          );
        }
      }
    }
    System.out.println(dp[n+2][0]);
  }
}