// Why am I so dumb? :c
// chrono::system_clock::now().time_since_epoch().count()
//#pragma GCC optimize("Ofast")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#include<bits/stdc++.h>
#include<ext/pb_ds/assoc_container.hpp>
#include<ext/pb_ds/tree_policy.hpp>
#include"trilib.h"
#define pb push_back
#define mp make_pair
#define all(x) (x).begin(), (x).end()
#define fi first
#define se second
using namespace std;
using namespace __gnu_pbds;
typedef long long ll;
template<typename T> using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
const int MAXN = (int)4e4 + 5;
int idx[MAXN];
void solve() {
int n = get_n();
for (int i = 1; i < n; ++i) {
idx[i] = i;
}
for (int i = 1; i < n; ++i) {
for (int j = i + 1; j < n; ++j) {
if (is_clockwise(n, idx[j], idx[i]) == 0) {
swap(idx[i], idx[j]);
}
}
}
vector<int> V;
V.pb(n);
V.pb(idx[n - 1]);
for (int i = n - 2; i > 0; --i) {
while (V.size() >= 2 && !is_clockwise(V[V.size() - 2], V.back(), idx[i])) {
V.pop_back();
}
V.pb(idx[i]);
}
if (!is_clockwise(V.back(), V.front(), V[1])) {
V.erase(V.begin());
}
/*
printf("Hull is:");
for (int x : V) {
printf(" %d", x);
}
printf("\n");
*/
give_answer(V.size());
}
int main() {
int tt = 1;
while (tt--) {
solve();
}
return 0;
}
