#!/bin/python3

import sys

def largestValue(A):
    x=[]
    # Return the largest value of any of A's nonempty subarrays.
    for i in range(len(A)):
        for j in range(i+1,len(A)):
            x.append(A[i]*A[j])
            print(A[i],A[j])
    return sum(x)

if __name__ == "__main__":
    n = int(input().strip())
    A = list(map(int, input().strip().split(' ')))
    result = largestValue(A)
    print(result)