#include "trilib.h"
#include "bits/stdc++.h"
using namespace std;
typedef int ll;
typedef unsigned long long ull;
typedef pair<ll,ll>pairll;
typedef pair<ll,ull>pairull;
typedef pair<ll,pairll>pair3l;
typedef long double ld;
typedef pair<ld,ld>pairld;
typedef pair<string,ll>pairsl;
#define fr first
#define sc second
#define pb push_back
#define endl '\n'
#define N 100007
#define MOD 1000000007
#define INF 10000000000007
#define eps 0.00000000001
#define A 50
#define PI 3.14159265359
ll n,d[40007],mn,mx;
deque<ll>v,a;
vector<ll>h;
map<pair3l,ll>m;
ll cl(ll x,ll y,ll z){
if(m[{x,{y,z}}]==0){
m[{x,{y,z}}]=ll(is_clockwise(x,y,z))+1;
}
return m[{x,{y,z}}]-1;
}
vector<ll> S(ll l,ll r){
vector<ll>k;
k.clear();
if(l==r){
k.pb(l);
return k;
}
ll m1=(l+r)/2;
vector<ll>k1=S(l,m1);
vector<ll>k2=S(m1+1,r);
ll x=0;
ll y=0;
while(x<k1.size() || y<k2.size()){
if(y==k2.size()){
k.pb(k1[x]);
x++;
}else if(x==k1.size()){
k.pb(k2[y]);
y++;
}else if(cl(1,k1[x],k2[y])==1){
k.pb(k1[x]);
x++;
}else{
k.pb(k2[y]);
y++;
}
}
return k;
}
int main(){
n=get_n();
if(n==3){
give_answer(3);
return 0;
}
vector<ll>k=S(2,n);
for(auto it:k){
v.pb(it);
}
a.pb(v[0]);
a.pb(v[1]);
// cout<<0<<" "<<v[0]<<endl;
//cout<<1<<" "<<v[1]<<endl;
ll x=2;
for(int i=2;i<n-1;i++){
//cout<<i<<" "<<v[i]<<endl;
while(x>1 && cl(a[x-2],a[x-1],v[i])==0){
x--;
a.pop_back();
}
x++;
a.pb(v[i]);
}
while(x>3 && (cl(a[x-1],a[0],a[1])==0 || cl(a[x-2],a[x-1],a[0])==0)){
if(cl(a[x-1],a[0],a[1])==0){
x--;
a.pop_front();
}else{
x--;
a.pop_back();
}
}
ll y=0;
for(int i=0;i<x;i++){
if(cl(a[i],1,a[(i+1)%x])==1)y++;
}
if(y>0){
give_answer(x-y+2);
}else give_answer(x);
return 0;
}
/*
8
15 10
1 18
4 16
6 14
7 11
6 8
4 4
1 1
7
-640171411 -194312902
-841925336 987730324
190043513 -997888031
-818099011 526395621
765098899 -53534033
-519211010 -921903684
749848805 -765518967
*/
