#include <bits/stdc++.h>
#define pb push_back
#define fi first
#define se second

using namespace std;
using ii = pair <int, int>;
using vi = vector <int>;

ii qry(vi &g){
    if (g.size() == 1) return ii(-1, -1);
    cout << "? " << g.size() << ' ';
    for (int u : g) cout << u << ' ';
    cout << endl;
    ii ans; cin >> ans.fi >> ans.se;
    return ans;
}

int main(){
    int n; cin >> n;

    vector <ii> edges;
    vector <vi> si;

    for (int f = 1; f <= n; ++ f){
        int lab = -1;
        vector <int> used(n + 1, 0);
        for (int j = 0; j < si.size(); j ++){
            vi ask = si[j];
            ask.pb(f);
            auto [u, v] = qry(ask);
            if (u == -1) lab = j;
            else {
                while (u != -1){
                    edges.pb({u, v});
                    used[u] = 1, used[v] = 1;
                    ask = {f};
                    for (int z : si[j]) if (!used[z]) ask.pb(z);
                    if (ask.size() == 1) break;
                    auto [g, k] = qry(ask);
                    u = g, v = k;
                }
            }
        }

        vi nw = {f};

        if (lab == -1) si.pb(nw);
        else si[lab].pb(f);
    }

    cout << "! " << edges.size() << endl;
    for (auto [u, v]: edges) cout << u << ' ' << v << endl;


    return 0;
}