https://codeforces.com/gym/102168/problem/F

#include <bits/stdc++.h>
#define all(x) (x).begin(),(x).end()

using namespace std;
using ll = long long;

int itr = 0;

char ask(const vector<int>& a, const vector<int>& b) {
    itr++;
    if (itr > 9) {
        while (true);
    }
    cout << "? " << a.size() << "\n";
    for (int val : a) {
        cout << val + 1 << ' ';
    }
    cout << '\n';
    for (int val : b) {
        cout << val + 1 << ' ';
    }
    cout << endl;
    char res;
    cin >> res;
    return res;
}

void PrintAnswer(int val) {
    cout << "! " << val + 1 << endl;
    exit(0);
}

void Solve(vector<int> arr, char bad) {
    if (arr.size() == 1) {
        PrintAnswer(arr[0]);
    } else if (arr.size() == 2) {
        if (ask({arr[0]}, {arr[1]}) == bad) {
            PrintAnswer(arr[1]);
        } else {
            PrintAnswer(arr[0]);
        }
    } else {
        vector<int> a, b;
        const int n = arr.size();
        int sz = n / 3 + ((n % 3 == 2) ? 1 : 0);
        for (int i = 0; i < sz; i++) {
            a.push_back(arr[i]);
            b.push_back(arr[i + sz]);
        }
        auto res = ask(a, b);
        if (res == '=') {
            vector<int> c;
            for (int i = 2 * sz; i < n; i++) {
                c.push_back(arr[i]);
            }
            Solve(c, bad);
        } else {
            if (res == bad) {
                Solve(b, bad);
            } else {
                Solve(a, bad);
            }
        }
    }
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    int n;
    cin >> n;
    vector<int> a, b, c, d;
    int sz = n / 3;
    for (int i = 0; i < sz; i++) {
        a.push_back(i);
        b.push_back(sz + i);
        c.push_back(sz * 2 + i);
    }
    for (int i = 3 * sz; i < n; i++) {
        d.push_back(i);
    }
    auto res1 = ask(a, b);
    if (res1 == '=') {
        auto res2 = ask(a, c);
        if (res2 == '=') {
            a.clear();
            for (int i = 0; i < d.size(); i++) {
                a.push_back(i);
            }
            Solve(d, ask(a, d));
        } else {
            Solve(c, res2);
        }
    } else {
        auto res2 = ask(c, a);
        if (res2 == '=') {
            Solve(b, res1);
        } else {
            Solve(a, res2);
        }
    }
}