#include<bits/stdc++.h> using namespace std; int main() { int t=1; // cin>>t; while(t--) { long long n; cin>>n; long long l=1,r=n-1,ans=n,pos=1; vector<long long> vi; while(l<=r) { long long mid=(l+r)/2; vi.push_back(mid),l=mid+1; } reverse(vi.begin(),vi.end()); for(int i=0;i<vi.size();i++) if(i%2==0) pos+=vi[i]; else pos-=vi[i]; cout<<"? "<<pos<<endl; fflush(stdout); string res; cin>>res; l=1,r=n-1; int cnt=0; if(pos-1<n-pos) cnt=1; while(l<=r) { long long mid=(l+r)/2; long long p=pos; if((++cnt)%2==0) p+=mid; else p-=mid; cout<<"? "<<p<<endl; fflush(stdout); cin>>res; if(res=="1") r=mid-1,ans=mid; else l=mid+1; pos=p; } cout<<"= "<<ans<<endl; fflush(stdout); } }