#include <bits/stdc++.h>
using namespace std;
#define pb push_back
#define fi first
#define se second
#define int long long int
#define pii pair<int,int>
const int INF= 1e15;
const int MAX=150000+5;
const int MAXK=20;
const int mod = 1e9+7;
int gcd(int a, int b)
{
    while(b>0)
    {
        a=a%b;
        swap(a,b);
    }
    return a;
}
int binpow(int a,int b)
{
    int res=1;
    while(b>0)
    {
        if(b%2==1)
            res=res*a%mod;
        a=a*a%mod;
        b/=2;
    }
    return res%mod;
}
int query(int i)
{
    cout<<"? "<<i<<endl;
    int res;
    cin>>res;
    return res;
}
void solve()
{
    int n;
    cin>>n;
    int l=1,r=n;
    while(l<r)
    {
        int mid=l+(r-l)/2;
        int a=query(mid);
        int b=query(mid+1);
        if(a<b)
        {
            r=mid;
        }
        else
        {
            l=mid+1;
        }
    }
    cout<<"! "<<l<<"\n";


}
int32_t main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
#ifndef ONLINE_JUDGE
   freopen("input.txt","r",stdin);
    freopen("output.txt","w",stdout);
#endif // ONLINE_JUDGE
    int t=1;
    //cin>>t;
    for(int i=1;i<=t;i++)
    {
        //cout<<"Case #"<<i<<": ";
        solve();
    }
}