// where is the root
#include<bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i=0; i<n; i++)
#define pb push_back
int n,a,b,adj[510];
vector<int> v;
char S[10];
int main(){
    cin>>n;
    rep(i,n-1){
        cin>>a>>b;
        adj[a]++;adj[b]++;
    }
    rep(i,n)if(adj[i]==1)v.pb(i);
    rep(i,n)if(adj[i]!=1)v.pb(i);
    int s=0,e=n,mid;
    while(e-s>1){
        mid=(e+s)/2;
        cout<<"? "<<mid<<' ';
        rep(i,mid)cout<<v[i]<<' ';
        cout<<endl;cout.flush();
        cin>>S;
        if(S[0]=='N')s=mid;
        else e=mid;
    }
    cout<<"! "<<v[e-1]<<endl;
}