#include <bitset>
#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#include <bits/stdc++.h>
#include <immintrin.h>
using namespace std;
typedef long long ll;
#define int ll
const int inf = int(1e18);
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef pair<int, int> p2;
#define rep(i, high) for (int i = 0; i < (high); i++)
#define repp(i, low, high) for (int i = (low); i < (high); i++)
#define repe(i, container) for (auto& i : container)
#define sz(container) ((int)container.size())
#define all(x) begin(x),end(x)
inline void fast() { cin.tie(0)->sync_with_stdio(0); }
#if _LOCAL
#define assert(x) if (!(x)) __debugbreak()
#endif
int n;
int numguess = 0;
#if 1 || !_LOCAL
int ask(int x)
{
cout << "? " << x << endl;
int resp;
cin >> resp;
return resp;
}
#else
int secret = -1;
void init()
{
mt19937 rng(time(0));
//secret = uniform_int_distribution<int>(1, n)(rng);
cout << "SECRET=" << secret << "\n";
}
int last = -1000;
int ask(int x)
{
numguess++;
if (secret == -1) init();
int ret;
if (last == -1000) ret = 0;
else
{
ret = abs(x - last) >= secret;
}
//cout << "ASK " << x << ",DIFF=" << abs(x - last) << " " << ret << "\n";
last = x;
return ret;
}
#endif
signed main()
{
fast();
/*vi nums;
int lo = 1;
int hi = 239578;
while (lo+1<hi)
{
int mid = (lo + hi) / 2;
nums.push_back(mid);
lo = mid;
}
repe(v, nums) cout << v << "\n";
int ans = 0;
rep(i, sz(nums)) ans += (i % 2 ? 1 : -1) * nums[i];
cout << ans << " " << abs(ans-hi/3);
cout << "";
return 0;*/
//n = int(1e9);
////cin >> n;
//if (n<=64)
//{
// rep(i, n / 2)
// {
// if (ask(i + 1) == 0 && i)
// {
// cout << "= " << abs(n-(i-1)-i+1)-1 << endl;
// return 0;
// }
// if (ask(n - i) == 0)
// {
// cout << "= " << abs(n - i - (i + 1)) + 1 << endl;
// return 0;
// }
// }
//}
auto solve = [&](int n)
{
if (n == 2)
{
int a = ask(1);
int b = ask(2);
if (b == 1)
{
cout << "= " << 1 << endl;
//assert(secret==1);
}
else cout << "= " << 2 << endl;
//assert(secret == 2);
return 0;
}
if (n <= 64)
{
rep(i, n / 2)
{
if (ask(i + 1) == 0 && i)
{
cout << "= " << abs(n - (i - 1) - i + 1) - 1 << endl;
//assert(secret == abs(n - (i - 1) - i + 1) - 1);
return 0;
}
if (ask(n - i) == 0)
{
cout << "= " << abs(n - i - (i + 1)) + 1 << endl;
//assert(secret == abs(n - i - (i + 1)) + 1);
return 0;
}
}
if (n % 2)
{
if (ask(n / 2 + 1) == 0)
{
cout << "= " << 2 << endl;
//assert(secret == 2);
return 0;
}
}
cout << "= 1" << endl;
//assert(secret == 1);
return 0;
}
vi nums;
{
int lo = 0;
int hi = n;
while (lo + 1 < hi)
{
int mid = (lo + hi) / 2;
nums.push_back(mid);
lo = mid;
}
}
int ma = 0;
int mi = n;
int ans = 0;
rep(i, sz(nums)) ans += (i % 2 ? 1 : -1) * nums[i], ma = max(ma, ans), mi = min(mi, ans);
//cout << ans << " " << abs(ans - hi / 3);
int par = ans > 0;
int s = -mi + 1;
ask(s);
int last = s;
int lo = 0;
int hi = n;
int ind = 0;
set<int> seen;
seen.insert(s);
auto valid = [&](int g)
{
if (g<0||g>n) return false;
if (seen.count(g)) return false;
return true;
};
vi tryv = { 0, 1,-1,2,-2 };
int direction = -1;
while (lo + 1 < hi)
{
int mid = (lo + hi) / 2;
//cout << (ind%2?"+":"-") << mid << "\n";
int g;
if (ind % 2) g = last + mid;
else g = last - mid;
/*if (direction==-1)
{
if (last - mid >= 1) g = last - mid;
else direction = 1, g = last + mid;
}
else
{
if (last + mid <= 1) g = last + mid;
else direction = -1, g = last - mid;
}*/
assert(valid(g));
seen.insert(g);
if (ask(g))
{
hi = mid;
}
else lo = mid;
last = g;
ind++;
}
cout << "= " << hi << endl;
//assert(hi == secret);
return 0;
};
cin >> n;// >> secret;
solve(n);
return 0;
/*n = 67;
secret = 44;
solve(n);
repp(i, 2, 1000)
{
repp(j, 1, i + 1)
{
n = i;
secret = j;
solve(n);
}
}*/
//cin >> n >> secret;*/
return 0;
}
