#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>
#include <string>
#include <cmath>
using namespace std;
long long a[110] , b[10010];
int main()
{
    int n;
    while( scanf( "%d" , &n ) != EOF )
    {
        for( int i=0 ; i<n ; i++ ) scanf( "%I64d" , &a[i] );
        int p = 0;
        for( int i=0 ; i<n ; i++ )
            for( int j=i+1 ; j<n ; j++ ) b[p++] = a[i] + a[j];
        sort( b , b + p );
        long long sum = 0 , now = b[0] - 1;
        for( int i=0 ; i<p ; i++ )
            if( now != b[i] )
            {
                now = b[i];
                sum += b[i];
            }
        printf( "%I64d\n" , sum );
    }
    return 0;
}