/*DavitMarg*/
#include <iostream>
#include <algorithm>
#include <cmath>
#include <vector>
#include <string>
#include <cstring>
#include <map>
#include <set>
#include <queue>
#include <iomanip>
#include <stack>
#include <cassert>
#include <iterator>
#include <bitset>
#include <fstream>
#ifndef death
#include<trilib.h>
#endif // death
#define mod 1000000007ll
#define LL long long
#define LD long double
#define MP make_pair
#define PB push_back
#define all(v) v.begin(),v.end()
using namespace std;
#ifdef death
int get_n()
{
cout<<"N::"<<endl;
int x;
cin>>x;
return x;
}
bool is_clockwise(int a, int b, int c)
{
cout<<":::"<<a<<" "<<b<<" "<<c<<endl;
int x;
cin>>x;
return x;
}
void give_answer(int x)
{
cout<<x<<endl;
}
#endif // death
map<pair<int,pair<int,int>>,bool> used,pre;
bool cw(int a,int b,int c)
{
if(used[MP(a,MP(b,c))])
return pre[MP(a,MP(b,c))];
used[MP(a,MP(b,c))]=1;
return pre[MP(a,MP(b,c))]=is_clockwise(a,b,c);
}
bool ccw(int a,int b,int c)
{
return !cw(a,b,c);
}
int convex(vector<int>& p)
{
vector<int> up,down;
int st,en;
reverse(all(p));
p.pop_back();
reverse(all(p));
p.pop_back();
vector<int> add=p;
p.clear();
p.PB(st);
for(int i=0;i<add.size();i++)
for(int j=0;j<add.size();j++)
p.PB(add[j]);
p.PB(en);
st=p[0];
en=p.back();
up.PB(p[0]);
down.PB(p[0]);
for(int i=1;i<p.size();i++)
{
if(i==p.size()-1 || cw(p[0],p[i],p[p.size()-1]))
{
while(up.size()>1 && !cw(up[up.size()-2],up[up.size()-1],p[i]) )
up.pop_back();
up.PB(p[i]);
}
if(i==p.size()-1 || ccw(p[0],p[i],p[p.size()-1]))
{
while(down.size()>1 && !cw(down[down.size()-2],down[down.size()-1],p[i]) )
down.pop_back();
down.PB(p[i]);
}
}
down.pop_back();
reverse(all(down));
down.pop_back();
for(int i=0;i<down.size();i++)
up.PB(down[i]);
return up.size();
}
int ans,n;
vector<int> p;
int main()
{
n=get_n();
for(int i=1;i<=n;i++)
p.PB(i);
for(int i=1;i<=n;i++)
for(int j=1;j<=n;j++)
{
if(i==j)
continue;
swap(p[1],p[i]);
swap(p[n],p[j]);
ans=max(ans,convex(p));
swap(p[1],p[i]);
swap(p[n],p[j]);
}
give_answer(ans);
return 0;
}
/*
*/
