E - Interview

#include <bits/stdc++.h>
 
using namespace std;
 
int query(int l, int r){
    cout << "? ";
    cout << (r - l + 1) << " ";
    for(int i = l; i <= r; i++){
        cout << i;
        if(i == r) cout << endl;
        else cout << " ";
    }
 
    int res;
    cin >> res;
    return res;
}
 
int main(){
    cin.tie(nullptr), ios::sync_with_stdio(false);
    int t;
    cin >> t;
    while(t--){
        int n;
        cin >> n;
        vector <int> a(n + 1);
        for(int i = 1; i <= n; i++){
            cin >> a[i];
            a[i] += a[i - 1];
        }
 
        int l = 1, r = n;
        while(l < r){
            int mid = (l + r) >> 1;
            if(query(l, mid) != a[mid] - a[l - 1]) r = mid;
            else l = mid + 1;
        }
 
        cout << "! " << l << endl;
    }
}