#include <bits/stdc++.h>
#include "trilib.h"
#define int long long
#define sz(a) (int)a.size()
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
using namespace std;
signed main() {
ios_base::sync_with_stdio(false); cin.tie(nullptr);
int n=get_n();
int root=0;
int x1,x2;
vector<int> a;
for (int i = 0; i < n; i++)
{
if(i==root) continue;
a.push_back(i+1);
}
sort(all(a), [root](int _a, int _b){ return is_clockwise(root+1,_a,_b); });
vector<int> conv;
conv.push_back(root+1);
conv.push_back(a[0]);
for (int i = 1; i < sz(a); i++)
{
while(true){
x2=conv.back();
conv.pop_back();
x1=conv.back();
if(is_clockwise(x1,x2,a[i])){
conv.push_back(x2);
break;
}
}
conv.push_back(a[i]);
}
give_answer(sz(conv));
return 0;
}
