ABC353C

#include <assert.h>
#include <bits/stdc++.h>
using namespace std;
#ifndef __DEBUG__
#define dbg(...) 42
#endif
template <class T> using mpq = priority_queue<T, vector<T>, greater<T>>;

using ll = long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using vl = vector<ll>;
using vi = vector<int>;

int main(int argc, char **argv)
{
    ll n;
    const ll mod = 1e8;
    cin >> n;
    vl a(n);
    for (auto &x : a)
        cin >> x, x %= mod;

    sort(a.begin(), a.end());
    vl acc(n + 1);
    for (ll i = 0; i < n; ++i)
        acc[i + 1] = acc[i] + a[i];

    ll ans = 0;
    for (ll i = 0; i < n; ++i) {
        ll lb = lower_bound(a.begin(), a.end(), mod - a[i]) - a.begin();
        ll inc = lb;
        ll fhalf = inc * a[i] + acc[inc];
        ll shalf = (n - inc) * a[i] + (acc[n] - acc[inc]) - mod * (n - inc);
        ans += fhalf + shalf - 2 * a[i] + (inc <= i ? mod : 0);
    }

    cout << ans / 2 << endl;
    return 0;
};