#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define ld long double
#define Test int T;cin>>T;while(T--)
#define PI acos(-1)
#define endl "\n"
#define fx(x) fixed<<setprecision(x)
#define sz(s) (int)s.size()
#define all(v) (v).begin(),(v).end()
#define allr(v) (v).rbegin(),(v).rend()
#define mem(a,n) memset((a),n,sizeof (a))
#define INF 1e9
#define ii pair<ll,ll>
ll gcd(ll x,ll y){return(!y?x:gcd(y,x%y));}
ll lcm(ll x,ll y){return x/gcd(x,y)*y;}
void file(){
#ifndef ONLINE_JUDGE
    freopen("in.txt", "r", stdin);
    freopen("out.txt", "w", stdout);
#else
    //freopen("bridges.in", "r", stdin);
    //freopen("bridges.out", "w", stdout);
#endif
}
void fast(){
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    file();
}
int dx[]= {-1,0,1,0};
int dy[]= {0,1,0,-1};
const double eps=1e-9;
const int mod=1e9+7;
const int N=1e5+5;
int a[N];
int ask(int i){
    if(a[i])return a[i];
    cout<<"? "<<i<<endl;
    cout.flush();
    int x;cin>>x;
    return a[i]=x;
}
int main(){
    fast();
    int n;
    cin>>n;
    a[0]=a[n+1]=1e9;
    int l=1,r=n;
    while(l<=r){
        int md=l+r>>1;
        int xl=ask(md);
        int xr=ask(md+1);
        if(xl>=xr){
            l=md+1;
        }
        else r=md-1;
    }
    cout<<"! "<<l<<endl;
    cout.flush();
    return 0;
}