#include <bits/stdc++.h>
#define f first
#define s second
#define mp make_pair
using namespace std;
typedef long long ll;
const ll mod = 1e9 + 7;
// Cope Counter = at least 142

pair<int, int> qry(set<int> pts) {
  cout << "? " << pts.size();
  for(int i : pts) cout << " " << i + 1;
  cout << "\n";
  cout.flush();
  pair<int, int> e;
  cin >> e.f >> e.s;
  if(e.f > e.s) swap(e.f, e.s);
  return e;
}

signed main() {
	ios::sync_with_stdio(0);
	cin.tie(0);
  int n;
  cin >> n;
  bool vis[n];
  for(int i = 0; i < n; i++) vis[i] = 0;
  set<int> bk[n];
  set<int> cur;
  vector<pair<int, int>> edges;
  vis[0] = 1, bk[0].insert(0);
  for(int i = 1; i < n; i++) {
    if(n > 1000) {
      bk[0].insert(i);
      auto e = qry(bk[0]);
      if(e.f >= 0) {
        bk[0].erase(i);
        bk[1].insert(i);
        edges.push_back(e);
      } else {
        bk[1].insert(i);
        e = qry(bk[1]);
        if(e.f >= 0) edges.push_back(e);
        bk[1].erase(i);
      }
      continue;
    }
    for(int j = 0; j < n; j++) {
      if(bk[j].empty()) {
        if(!vis[i]) {
          vis[i] = 1;
          bk[j].insert(i);
        }
        break;
      }
      bk[j].insert(i);
      auto e = qry(bk[j]);
      if(e.f < 0) {
        if(!vis[i]) vis[i] = 1;
        else bk[j].erase(i);
        continue;
      }
      cur = bk[j];
      bk[j].erase(i);
      while(e.f >= 0) {
        edges.push_back(e);
        cur.erase(e.f - 1);
        if(cur.size() < 2) break;
        e = qry(cur);
      }
    }
  }
  cout << "! " << edges.size() << "\n";
  for(auto i : edges) cout << i.f << " " << i.s << "\n";
  cout.flush();
}