#include<bits/stdc++.h>
#define rep(i,a,b) for(int i=a;i<=b;i++)
#define pre(i,a,b) for(int i=a;i>=b;i--)
#define N 100005
using namespace std;
int n;
int main(){
	scanf("%d",&n);
	int l=1,r=n;
	while(l<r){
		int mid=(l+r)>>1,x,y;
		cout<<"? "<<mid<<endl;cin>>x;
		if(mid==n)y=114514;else cout<<"? "<<mid+1<<endl,cin>>y;
		if(x<y)r=mid;else l=mid+1;
	}
	cout<<"! "<<l<<endl;
	return 0;
}
