#include "trilib.h"
#include <iostream>
#include <cstdio>
#include <algorithm>
#include <vector>
#include <deque>
using namespace std;
#define endl '\n'
#define ll long long
#define pi pair<int, int>
#define f first
#define s second
int n;
vector<int> a[2];
deque<int> v;
int main(){
ios::sync_with_stdio(0);
cin.tie(0);
n = get_n();
a[0] = {1, 2};
for(int i = 3; i <= n; i++){
a[is_clockwise(1, 2, i)].push_back(i);
}
n = 0;
for(int t = 0; t < 2; t++){
sort(a[t].begin() + !t, a[t].end(), [&](int x, int y){
return is_clockwise(1, x, y);
});
for(int i : a[t]){
while(n > 1 && !is_clockwise(v[n - 2], v[n - 1], i)) v.pop_back(), n--;
v.push_back(i), n++;
}
}
hell:
if(n > 2 && !is_clockwise(v[n - 2], v[n - 1], v[0])){
v.pop_back(), n--;
goto hell;
}
if(n > 2 && is_clockwise(v[1], v[0], v[n - 1])){
v.pop_front(), n--;
goto hell;
}
give_answer(n);
return 0;
}
