逆向思维

void solve()
{
    int n;
    cin >> n;
    int ans = 0;
    for (int i = 1; i <= n; i++) ans += (1 + n - i + 1) * (n - i + 1) / 2;
    map<int, int> p;
    for (int i = 1; i <= n; i++)
    {
        int x;
        cin >> x;
        if (p[x])
        {
            ans -= (n - i + 1) * p[x];
        }
        p[x] = i;
    }
    cout << ans << '\n';
}