/* package whatever; // don't place package name! */
 
import java.util.*;
import java.lang.*;
import java.io.*;
 
/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
		// your code goes here
		int[] a = {2, -1, 3, 4};
		int n = a.length;
		int k = 2;
		int[] dp = new int[n];
		dp[1] = a[0] * a[1];
 
		for(int i = 2; i < n; i++){
			dp[i] = a[i] * a[i-1];
			int u = 0;
			for(int j = Math.max(u, i - k); j <= i-1; j++){
				dp[i] = Math.min(dp[i], a[i] * a[j] + dp[j]);
			}
		}
		System.out.print(dp[n-1]);
	}
}

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