#include <bits/stdc++.h>   using namespace std;   #define INF 1000000009      int get(int i){       cout <<  ?   << i+1 << endl;       cout.flush();       int a; cin >> a;       int b;       if(i == 0) b = INF;       else{           cout <<  ?   << i << endl;           cout.flush();           cin >> b;       }       return b-a;   }      int main(){       // freopen( input.txt ,  r , stdin);       // freopen( output.txt ,  w , stdout);       ios_base::sync_with_stdio(false);       cin.tie(0);       int n; cin >> n;       if(n == 1){           cout <<  !   << 1 << endl;           cout.flush();           return 0;       }       if(get(1) < 0){           cout <<  !   << 1 << endl;           cout.flush();           return 0;       }       if(get(n-1) > 0){           cout <<  !   << n << endl;           cout.flush();           return 0;       }       int lo = 0, hi = n-1;       while(lo < hi){           int mid = lo+(hi-lo)/2;           if(get(mid) > 0) lo = mid+1;           else hi = mid;       }       cout <<  !   << lo << endl;       cout.flush();   }