Atcoder Dp Problem

help
1

Hi, i am new to Dp and trying to learn. i started solving atcoder educational dp contest but in the first problem i got stuck. can someone please help me

2

import java.util.Scanner;

public class AtCoder_A {
// public static int minSum;

public static int minCostDp(int a[],int n){
    int dp[] = new int[n+1];
    dp[1] = 0;
    dp[2] = Math.abs(a[2]-a[1]);
    for(int i=3;i<=n;i++){
        dp[i] = Math.min(dp[i-1]+Math.abs(a[i]-a[i-1]),dp[i-2]+Math.abs(a[i]-a[i-2]));
    }
    return dp[n];
}
public static int minCostRecursive(int a[],int n,int i,int j,int minSum){
    if(j==n)
        return minSum+Math.abs(a[j]-a[i]);

    if(j>n)
        return Integer.MAX_VALUE;

    minSum = minSum+Math.abs(a[i]-a[j]);
    i=j;
    int ans1 = minCostRecursive(a,n,i,j+1,minSum);
    int ans2 = minCostRecursive(a,n,i,j+2,minSum);
    return Math.min(ans1,ans2);
}
public static void main(String args[]){
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int a[] = new int[n+1];
    for(int i=1;i<=n;i++){
        a[i] = sc.nextInt();
    }

    //System.out.println(minCostRecursive(a,n,1,1,0));
    System.out.println(minCostDp(a,n));

}

}

3

this is my code. it is giving ce in atcoder. i am very new to atcoder. and unable to get why it is giving ce