#include <bits/stdc++.h> using namespace std; int query( long long c ) { cout << "? " << c << endl; int ans; cin >> ans; return ans; } void answer( long long c ) { cout << "= " << c << endl; } int main() { long long n; cin >> n; long long l = 0, r = n; while ( r - l > 1 ) { long long c = (l + r) / 2; query( 1 ); if ( query( c + 1 ) ) r = c; else l = c; } answer( r ); return 0; }