#define _USE_MATH_DEFINES
#include "bits/stdc++.h"
using namespace std;
#define FOR(i,j,k) for(int (i)=(j);(i)<(int)(k);++(i))
#define rep(i,j) FOR(i,0,j)
#define each(x,y) for(auto &(x):(y))
#define mp make_pair
#define MT make_tuple
#define all(x) (x).begin(),(x).end()
#define debug(x) cout<<#x<<": "<<(x)<<endl
#define smax(x,y) (x)=max((x),(y))
#define smin(x,y) (x)=min((x),(y))
#define MEM(x,y) memset((x),(y),sizeof (x))
#define sz(x) (int)(x).size()
#define RT return
using ll = long long;
using pii = pair<int, int>;
using vi = vector<int>;
using vll = vector<ll>;

int query(int x, int y) {
    if (y == 0)return x;
    cout << "? " << x << ' ' << y << endl;
    int res;
    cin >> res;
    return res;
}

int N;
vi lost[301];

// (l, r]
int f(int l, int r) {
    if (r - l == 1) {
        if (r > N)return 0;
        else return r;
    }
    int m = (l + r) / 2;
    int x = f(l, m);
    int y = f(m, r);
    int res = f(x, y);
    lost[res].push_back(res^x^y);
    return res;
}

void solve() {
    cin >> N;
    int n = 1;
    while (n < N)n *= 2;
    int champ = f(0, n);
    int sec = lost[champ][0];
    FOR(i, 1, sz(lost[champ])) {
        sec = query(sec, lost[champ][i]);
    }
    cout << "! " << sec << endl;
}

int main() {
	solve();
	return 0;
}