import java.util.Scanner;

class CalDifference{

	public static void main(String[] k){
	
	int n, sumOfSq, sqOfSums, diff;
	int[] num; 
	int[] numSq;	

	Scanner sc = new Scanner(System.in);
	
	System.out.println("Enter the num of Elements to be entered");
	n = sc.nextInt();
	
	num = new int[n];
	numSq = new int[n];

	inputElements(num,n);
	sqOfElements(num,numSq,n);
	sumOfSq  = sum(numSq,n) * sum(numSq,n);
	sqOfSums = sum(num,n) * sum(num,n);	
	diff     = sumOfSq - sqOfSums;

	}

	public static void inputElements(int[] a, int n){

		Scanner sc = new Scanner(System.in);

		for(int i=0 ; i<n ; i++)
		{
		a[i] = sc.nextInt();
		}
	}
	
	public static void sqOfElements(int[] a,int[] aSq, int n){

	Scanner sc = new Scanner(System.in);
		
		for(int i=0 ; i<n ; i++)
		{
		aSq[i] = a[i] * a[i];
		}
	}

	public static int sum(int[] a, int n){
		
	int sum = 0;

		for(int i=0 ; i<n ; i++)
		{
		sum = sum + a[i];
		}
	return sum;
	}
}