#include <stdio.h>
void main(void){
    int n = 0 ;
    scanf("%d",&n);
    int numList[n] = {};
    for(int i = 0 ; i < n ; i++ ){
        scanf("%d",&numList[i]);
    }
    long int result = 0 ;  
    for(int i = 0 ; i < n ; i++ ){
        for(int j= 0 ; j < n ; j++ ){
             double ansA = i - j;
            if(ansA > 0 ){
               ansA *= -1;
            }
        
            double ansB = numList[i] - numList[j];
            if(ansB> 0 ){
               ansB *= -1;
            } 
            result += ansA*ansB;
        }
    }
    printf("%d",result);
}