#include "trilib.h"
#include <bits/stdc++.h>
#include <bits/extc++.h>
#define StarBurstStream ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
#define iter(a) a.begin(), a.end()
#define riter(a) a.rbegin(), a.rend()
#define lsort(a) sort(iter(a))
#define gsort(a) sort(riter(a))
#define pb(a) push_back(a)
#define eb(a) emplace_back(a)
#define pf(a) push_front(a)
#define ef(a) emplace_front(a)
#define pob pop_back()
#define pof pop_front()
#define mp(a, b) make_pair(a, b)
#define F first
#define S second
#define mt make_tuple
#define gt(t, i) get<i>(t)
#define tomax(a, b) ((a) = max((a), (b)))
#define tomin(a, b) ((a) = min((a), (b)))
#define topos(a) ((a) = (((a) % MOD + MOD) % MOD))
#define uni(a) a.resize(unique(iter(a)) - a.begin())
#define printv(a, b) {bool pvaspace=false; \
for(auto pva : a){ \
if(pvaspace) b << " "; pvaspace=true;\
b << pva;\
}\
b << "\n";}
using namespace std;
using namespace __gnu_pbds;
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using pdd = pair<ld, ld>;
using tiii = tuple<int, int, int>;
const ll MOD = 1000000007;
const ll MAX = 2147483647;
template<typename A, typename B>
ostream& operator<<(ostream& o, pair<A, B> p){
return o << '(' << p.F << ',' << p.S << ')';
}
ll ifloor(ll a, ll b){
if(b < 0) a *= -1, b *= -1;
if(a < 0) return (a - b + 1) / b;
else return a / b;
}
ll iceil(ll a, ll b){
if(b < 0) a *= -1, b *= -1;
if(a > 0) return (a + b - 1) / b;
else return a / b;
}
int main(){
StarBurstStream
int n = get_n();
vector<int> a, b;
for(int i = 3; i <= n; i++){
if(is_clockwise(2, 1, i)) a.eb(i);
else b.eb(i);
}
auto comp = [&](int i, int j){
return !is_clockwise(1, i, j);
};
sort(iter(a), comp);
sort(iter(b), comp);
a.eb(1);
b.eb(2);
// printv(a, cerr);
// printv(b, cerr);
deque<int> hull;
auto add = [&](int id){
while(hull.size() >= 2 && is_clockwise(hull[hull.size() - 2], hull.back(), id)){
hull.pob;
}
hull.eb(id);
};
for(int i : a) add(i);
for(int i : b) add(i);
// printv(hull, cerr);
for(int i = 0; i < n; i++){
int id = hull.front();
hull.pof;
add(id);
}
// printv(hull, cerr);
cout << hull.size() << "\n";
return 0;
}
