#include <bits/stdc++.h>
using namespace std;
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
//#define int long long
#include "trilib.h"
typedef pair<int,int> pii;
typedef vector<int> vi;
typedef vector<pii> vii;
typedef vector<bool> vb;
typedef long long ll;
typedef pair<ll,ll> pll;
typedef vector<pll> vll;
typedef tree<pii,null_type,less<pii>,rb_tree_tag,
tree_order_statistics_node_update> oset;
#define fi first
#define se second
#define pb push_back
#define pf push_front
#define mid (l+r)/2
#define all(x) x.begin(),x.end()
#define FOR(i,a) for(int i=0;i<(a);i++)
#define FORE(i,a,b) for(int i=(a);i<(b);i++)
#define cont(x) for(auto el:x) cout<<el<<' ';cout<<endl;
#define contp(x) for(auto el:x) cout<<el.fi<<'-'<<el.se<<' ';cout<<endl;
#define sp <<" "<<
#define DEBUG(x) cout<<(#x) sp x<<endl
#define carp(a,b) (((a%MOD)*(b%MOD))%MOD)
#define topla(a,b) (((a%MOD)+(b%MOD))%MOD)
const ll INF=1e18;
const int MAXN=92;//1e5+5;
const int MAXNN=2e5+5;
const int MOD=1e9+7;
signed main(){
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
int n=get_n();
if(n==3) give_answer(3);
else{
bool f=is_clockwise(1,2,3);
vi vec;
if(f){
vec.pb(1); vec.pb(2); vec.pb(3);
}
else{
vec.pb(3);vec.pb(2);vec.pb(1);
}
FORE(i,4,n+1){
FOR(j,vec.size()){
int once=(j-1>=0?j-1:vec.size()-1);
int sonra=(j+1<vec.size()?j+1:0);
//cout<<"here" sp once sp j sp sonra<<endl;
int bir=(is_clockwise(vec[once],vec[j],i)==true);
int iki=(is_clockwise(vec[j],vec[sonra],i)==true);
if(bir+iki==2) continue;
if(bir+iki==0){
vec[j]=i;
break;
}
else if(bir==0){
auto it=vec.begin()+j;
vec.insert(it,i);
break;
}
}
//cout<<"VEC"<<endl;
//cont(vec);
}
int ans=vec.size();
give_answer(ans);
}
}
