java我的动态编程解决方案（Kefa和第一步）在codeforces中有什么问题？

Question

我是动态规划方面的新手，我尝试解决codeforces中的问题，称为（Kefa和First steps），这是codeforces http://codeforces.com/contest/580/problem/A中问题的链接 这是我的解决方案我不知道我的代码出了什么问题有人能帮我吗

    package problemsolvingg;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.Scanner;
    public class mege {
        public static int[] arr;
        public static int[][] dp;
        public static int n;

        public static void clr(int n) {
            for(int i = 0 ; i < n ; i++) {
               for(int j = 0 ; j<n;j++) {
                   dp[i][j] = -1;
               }
            }
        }
        public static void main(String[] args) {
            // TODO Auto-generated method stub
          Scanner sc = new Scanner(System.in);
           n = sc.nextInt();  arr = new int[n]; dp = new int[n][n];
          clr(n);
          for(int i = 0 ; i < n  ; i++) {
              arr[i] = sc.nextInt();
          }
          int result = longSubsequence(1,0);
          System.out.println(result);

        }

        public static int longSubsequence(int i , int prev) {
            if(i == n)return 0;

             if(dp[i][prev] != -1)return dp[i][prev];
            int choice1 = longSubsequence(i+1 , prev);
            int choice2 = 0;

            if(arr[i] >= arr[prev] && (prev + 1 == i)) {
                choice2 = longSubsequence(i+1 , i) + 1;

            }
             return dp[i][prev] = Math.max(choice1, choice2);
        }
    }