#include<bits/stdc++.h>
#define L(i, j, k) for(int i = (j); i <= (k); ++i)
#define R(i, j, k) for(int i = (j); i >= (k); --i)
#define ll long long
#define sz(a) ((int) (a).size())
#define vi vector < int > 
#define me(a, x) memset(a, x, sizeof(a))
#define ull unsigned long long
#define ld __float128
using namespace std;
const int N = 2007;
int n;
int vis[N][N];
bool ask(vi &cur) {
	cout << "? " << sz(cur) << ' ';
	for(auto &t : cur) cout << t << ' ';
	cout << endl;
	int x, y;
	cin >> x >> y;
	if(x == -1) return 0;
	vis[x][y] = vis[y][x] = 1;
	return 1;
}
int inq[N];
void solve(vi S) {
	if(!sz(S)) return ; 
	int u = S[0];
	vi cur = {u};
	for(auto &x : S) if(x != u) {
		cur.emplace_back(x);
		if(ask(cur)) cur.pop_back();
	}
	for(auto &p : S) inq[p] = 1;
	for(auto &u : cur) inq[u] = 0;
	vi ncur;
	for(auto &p : S) if(inq[p]) {
		ncur.emplace_back(p);
		while(true) {
			vi np = vi{p};
			for(auto &k : cur) 
				if(!vis[p][k]) 
					np.emplace_back(k);
			if(sz(np) == 1 || !ask(np)) {
				break;
			}
		}
	}
	solve(ncur);
}
int main() {
	ios :: sync_with_stdio(false); 
	cin.tie(0); cout.tie(0);
	cin >> n;
	vi S;
	L(i, 1, n) S.emplace_back(i);
	solve(S); 
	int ans = 0;
	L(i, 1, n) L(j, i + 1, n) if(vis[i][j]) ++ans;
	cout << "! " << ans << '\n';
	L(i, 1, n) L(j, i + 1, n) if(vis[i][j]) cout << i << ' ' << j << '\n';
	cout << endl;
	return 0;
}