#include<bits/stdc++.h>
#include"trilib.h"
using namespace std;
int root;
bool cmp(int x, int y){
return is_clockwise(root, x, y);
}
vector<int> getstv(vector<int> v, int st, int en){
root = st;
sort(v.begin(), v.end(), cmp);
vector<int> stv;
stv.push_back(st);
for(auto x: v){
while(stv.size() > 1 && is_clockwise(stv.end()[-2], stv.end()[-1], x) == false)
stv.pop_back();
stv.push_back(x);
}
return stv;
}
int main(){
int n = get_n();
int a = 3;
int b = 6;
vector<int> l, r;
for(int i = 1; i<= n; i++){
if(i == a)
continue;
if(i == b)
continue;
if(is_clockwise(a, b, i) == false)
l.push_back(i);
else
r.push_back(i);
}
///L ARE ORDINEA DE LA A LA B, R DE LA B LA A
vector<int> stvl = getstv(l, a, b);
vector<int> stvr = getstv(r, b, a);
if(l.size() == 0){
int x = a;
while(stvr.size() > 1 && is_clockwise(stvr.end()[-2], stvr.end()[-1], x) == false)
stvr.pop_back();
stvr.push_back(x);
give_answer(stvr.size());
return 0 ;
}
if(r.size() == 0){
int x = b;
while(stvl.size() > 1 && is_clockwise(stvl.end()[-2], stvl.end()[-1], x) == false)
stvl.pop_back();
stvl.push_back(x);
give_answer(stvl.size());
return 0 ;
}
int fixed;
if(stvl.size() < stvr.size())
swap(stvl, stvr);
vector<int> cstvl = stvl;
for(auto x: stvr){
while(cstvl.size() > 1 && (x == cstvl.end()[-1] || is_clockwise(cstvl.end()[-2], cstvl.end()[-1], x) == false))
cstvl.pop_back();
}
fixed = cstvl.back();
int poz = cstvl.size();
vector<int> stv;
stv.push_back(fixed);
for(int i = poz; i < stvl.size(); i++){
int x = stvl[i];
while(stv.size() > 1 && (x == stv.end()[-1] || is_clockwise(stv.end()[-2], stv.end()[-1], x) == false))
stv.pop_back();
stv.push_back(x);
}
for(auto x: stvr){
while(stv.size() > 1 && (x == stv.end()[-1] || is_clockwise(stv.end()[-2], stv.end()[-1], x) == false))
stv.pop_back();
stv.push_back(x);
}
for(int i = 0; i < poz - 1; i++){
int x = stvl[i];
while(stv.size() > 1 && (x == stv.end()[-1] || is_clockwise(stv.end()[-2], stv.end()[-1], x) == false))
stv.pop_back();
stv.push_back(x);
}
give_answer(stv.size());
}
