#include <bits/stdc++.h>
#include "trilib.h"
#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx2")
#define int long long
#define pii pair<int,int>
#define vi vector<int>
#define ff first
#define ss second
#define sp << " " <<
#define all(x) x.begin(),x.end()
#define big(x) ((int)(x.size()))
using namespace std;
const int MOD = 1e9+7, LIM = 1e6+1, inf = 2e9;
const int N = 1e5+1;
void solve() {
int n = get_n();
vi poly = {1,2,3};
if (!is_clockwise(1,2,3)) reverse(all(poly));
int h = 3;
for (int i=4;i<=n;i++) {
vi low;
for (int j = 0;j<h;j++) {
if (!is_clockwise(i,poly[j],poly[(j+1)%h])) low.push_back(j);
}
if (low.empty()) continue;
int con = -1,con2 = -1;
for (int j = 0;j<big(low);j++) {
int nxt = poly[(low[j]+1)%h];
int prv = poly[(low[j]+h-1)%h];
int ths = poly[low[j]];
if (is_clockwise(i,nxt,ths) &&
!is_clockwise(i,ths,prv)) con = ths;
}
for (int j = big(low)-1;j>=0;j--) {
int nxt = poly[(low[j]+2)%h];
int prv = poly[low[j]%h];
int ths = poly[(low[j]+1)%h];
if (!is_clockwise(i,prv,ths) &&
is_clockwise(i,ths,nxt)) con2 = ths;
}
assert(con != -1 && con2 != -1);
vi to_del;
int p = find(all(poly),con)-poly.begin();
for (int j = (p+1)%h;poly[j] != con2;j=(j+1)%h) to_del.push_back(poly[j]);
for (auto it : to_del) poly.erase(find(all(poly),it));
poly.insert(find(all(poly),con)+1,i);
h = big(poly);
}
give_answer(h);
}
signed main() {
ios_base::sync_with_stdio(0); cin.tie(0);
#ifdef Dodi
freopen("in.txt", "r", stdin);
freopen("out.txt", "w", stdout);
#endif
int t = 1;
//cin >> t;
while (t --> 0) solve();
}
