solution1

#include<bits/stdc++.h>

using namespace std;

//---------------------------Hello there----------------------------

int n;
int a[20];
int dp[10][1 << 20];

int bestPairing(int board, int mask) {
    if(board == n + 1) return 0; // base case
    if(dp[board][mask] != -1) {
        return dp[board][mask]; // if ans already found in dp arr the return
    }

    // if ans not already computed, then compute
    int ans = 0;
    for (int i = 0; i < 2 * n; ++i) {
        for (int j = 0; j < 2 * n; ++j) {
            if( (mask & ((1 << i) | (1 << j))) == 0 )
                ans = max(ans, board * abs(a[i] - a[j]) * gcd(a[i], a[j]) + bestPairing(board + 1, mask | (1 << i) | (1 << j)));
        }
    }
    dp[board][mask] = ans; // store ans and then return
    return dp[board][mask];
}

int main() {

    cin >> n;
    for (int i = 0; i < 2 * n; ++i) {
        cin >> a[i];
    }
    memset(dp, -1, sizeof dp);
    cout << bestPairing(1, 0) << endl;

    return 0;
}