#include<bits/stdc++.h>
#define ll long long
#define F first
#define S second
#define in insert
#define er erase
#define pb push_back
#define ppb pop_back()
#define ph push
#define pp pop()
#define d3 ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define cans cout << ans << "\n";
#define yes cout << "YES" << "\n";
#define no cout << "NO" << "\n";
#define pll pair<ll,ll>
#define lin cout << "\n";
#define sqr 340
#define mod 1000000007
#define mid ((l+r)/2)
using namespace std;
ll fp(ll x , ll y)
{
if(y==0)
return 1;
ll z = fp(x,y/2);
if(y&1)
return z*z*x;
else
return z*z;
}
int sqrot(ll x)
{
int l = 0 , r = INT_MAX;
while(l<=r)
{
if(mid*mid>=x)
r=mid-1;
else
l=mid+1;
}
return r+1;
}
ll cel(ll x , ll y)
{
return x/y + bool(x/y);
}
string tb(ll x)
{
string s = "";
while(x>0)
{
if(x&1)
s+='1';
else
s+='0';
x/=2;
}
while(s.size()<60)
s+='0';
return s;
}
ll fb(string s)
{
ll x = 0;
ll c = 1;
for(int8_t i = 0 ; 60>i ; i++)
{
if(s[i]=='1')
x+=c;
c*=2;
}
return x;
}
int main()
{
ll n;
cin >> n;
ll l = 0 , r = n;
ll ans = 1;
while(l<=r)
{
ll x = 2*mid+1;
if(x<=0||x<=ans)
{
l=mid+1;
continue;
}
if(x>n)
{
r=mid-1;
continue;
}
bool ex = 0;
for(int i = 1 ; n-x+1>=i ; i++)
{
cout << "? " << i << " " << i+x-1 << "\n";
bool e;
cin >> e;
if(e)
{
ex=1;
break;
}
}
if(ex)
{
l=mid+1;
ans=max(ans,x);
}
else
r=mid-1;
}
l = 0 , r = n;
while(l<=r)
{
ll x = 2*mid;
if(x<=0||x<=ans)
{
l=mid+1;
continue;
}
if(x>n)
{
r=mid-1;
continue;
}
bool ex = 0;
for(int i = 1 ; n-x+1>=i ; i++)
{
cout << "? " << i << " " << i+x-1 << "\n";
bool e;
cin >> e;
if(e)
{
ex=1;
break;
}
}
if(ex)
{
l=mid+1;
ans=max(ans,x);
}
else
r=mid-1;
}
cout << "! " << ans << "\n";
}
