#include<iostream>
#include<string.h>
#include<algorithm>
#include<math.h>
#include<vector>
#include<map>
#include<queue>
#include<set> 
#include<stack>
#include<bitset>
#include<unordered_map>
#include<iomanip>
#define endl '\n'
#define pb push_back
#define debug(x) cout<<x<<endl; 
#define me(a,x) memset(a,x,sizeof(a))
#define L(i,j,k) for(int i=(j);i<=(k);++i)
#define R(i,j,k) for(int i=(j);i>=(k);--i)
#define int long long 
using namespace std;
typedef long long ll;
typedef pair<int ,int > PII;
typedef unsigned long long ull;
int a[55];
signed main(){
	
	int n;cin>>n;
	int l=1,r=n;
	L(i,1,n){
		int mid=l+r>>1;
		printf("? %d\n",mid);
		cout.flush();
		scanf("%d",&a[i]);
		if(a[i]>a[i-1])l=mid+1;
		else r=mid-1;
		if(a[i]==a[i-1]){
			printf("! %d",mid);
			return 0;
		}
	}
	
}