#include "trilib.h"
#include <algorithm>
#include <bits/stdc++.h>
using namespace std;
#define ll int
#define ff first
#define ss second
#define ln "\n"
const ll INF = 2e9;
void solve(){
ll n = get_n();
vector<ll> perm;
for (ll i=1; i<=n; i++){
perm.push_back(i);
}
ll x = perm[0], y = perm[1];
vector<ll> left, right;
for (ll i=2; i<n; i++){
if (is_clockwise(x, y, perm[i])) right.push_back(perm[i]);
else left.push_back(perm[i]);
}
sort(right.begin(), right.end(), [&](ll i1, ll i2){
if (i1==i2) return 0;
return is_clockwise(x, i1, i2);
});
sort(left.begin(), left.end(), [&](ll i1, ll i2){
if (i1==i2) return 0;
return is_clockwise(x, i1, i2);
});
vector<ll> ord;
for (auto z:left) ord.push_back(z);
ord.push_back(y);
for (auto z:right) ord.push_back(z);
deque<ll> hull;
hull.push_back(x);
hull.push_back(ord[0]);
for (ll i=1; i<n-1; i++){
while (hull.size()>1 and !is_clockwise(hull[hull.size()-2], hull[hull.size()-1], ord[i])) hull.pop_back();
hull.push_back(ord[i]);
}
while (hull.size()>3){
if (!is_clockwise(hull.back(), hull[0], hull[1])){
hull.pop_front();
}else if (!is_clockwise(hull[hull.size()-2], hull.back(), hull[0])){
hull.pop_back();
}else break;
}
give_answer(hull.size());
}
int main(){
ios_base::sync_with_stdio(false);
cin.tie(nullptr); ll t=1;
// cin >> t;
while (t--) solve();
}
