int bestTrio(int n, vector<int> ta, vector<int> tb) {
    vector<int> a[n + 1];
    for(int i = 0; i < ta.size(); i++) {
        a[ta[i]].push_back(tb[i]);
        a[tb[i]].push_back(ta[i]);
    }
    for(int i = 1; i <= n; i++) {
        sort(a[i].begin(), a[i].end());
    }
    int mn = 4 * n;
    int l = 0,r = 0;
    auto fun = [&] (int p1, int p2, int p3) {
        mn = min(mn, (int)a[p1].size() + (int)a[p2].size() + (int)a[p3].size() - 6);
    };
    for(int i = 1; i <= n; i++) {
        for(auto j : a[i]) {
            l = 0, r = 0;
            while(l < a[i].size() && r < a[j].size()) {
                if(a[i][l] < a[j][r]) {
                    l++;
                } else if(a[i][l] > a[j][r]) {
                    r++;
                } else {
                    fun(i, j, a[i][l]);
                    l++;
                    r++;
                }
            }
        }
    }
    return (mn == 4 * n ? -1 : mn);
}