#include <bits/stdc++.h>
#define ll long long
using namespace std;

int query(ll l,ll r)
{
	printf("? %lld %lld\n",l,r);
	fflush(stdout);
	int res;
	cin>>res;
	return res;
}
int main()
{
    ll n;
    scanf("%lld",&n);
	ll lef = 1, rig = n,ans=-1;
	while(lef<=rig)
	{
		ll mid = (lef+rig)>>1;
		int res = query(lef,mid);
		if(res==1) rig = mid-1,ans=mid;
		else lef = mid+1;
	}
    printf("! %lld\n",ans);
    return 0;
}