#include <bits/stdc++.h> 
using namespace std;
using ll =long long;
#define all(v) v.begin(),v.end()
 #define rep(i,a,b) for(int i=a;i<b;i++)
#define rrep(i,a,b) for(int i=a;i>=b;i--)


int main() {
ll N;cin>>N;
for(ll i=1;i<=N;i+=2) {
  cout<<"? "<<i<<" "<<i+1<<endl;
  ll z;cin>>z;
  if(z==i) {
    cout<<"! "<<i+1<<endl;
    return 0;
  }
  else if(z==i+1) {
    cout<<"! "<<i<<endl;
    return 0;

  }
}

cout<<"! "<<N<<endl;
}