#include "trilib.h"
#include<bits/stdc++.h>
using namespace std;
int n;
/*
int get_n()
{
cin>>n;
return n;
}
bool is_clockwise(int i,int j,int k)
{
cout<<i<<" "<<j<<" "<<k<<" -> ";
int ret;
cin>>ret;
return ret;
}
void give_answer(int sz)
{
cout<<sz<<endl;
}
*/
set<int> hull;
vector<int> points[2];
bool cmp(int a,int b)
{
return is_clockwise(a,1,b);
}
stack<int> hulls[2];
bool pop_wrong()
{
int was=points[0].size()+points[1].size();
/*
for(auto k:points[0])cout<<k<<" ";cout<<endl;
for(auto k:points[1])cout<<k<<" ";cout<<endl;
*/
while(points[0].size()>=2&&is_clockwise(points[1][0],points[0][points[0].size()-1],points[0][points[0].size()-2])==1)points[0].pop_back();
/*
for(auto k:points[0])cout<<k<<" ";cout<<endl;
for(auto k:points[1])cout<<k<<" ";cout<<endl;
*/
while(points[1].size()>=2&&is_clockwise(points[0][0],points[1][points[1].size()-1],points[1][points[1].size()-2])==1)points[1].pop_back();
reverse(points[0].begin(),points[0].end());
reverse(points[1].begin(),points[1].end());
while(points[0].size()>=2&&is_clockwise(points[1][0],points[0][points[0].size()-1],points[0][points[0].size()-2])==0)points[0].pop_back();
while(points[1].size()>=2&&is_clockwise(points[0][0],points[1][points[1].size()-1],points[1][points[1].size()-2])==0)points[1].pop_back();
reverse(points[0].begin(),points[0].end());
reverse(points[1].begin(),points[1].end());
int is=points[0].size()+points[1].size();
return was>is;
}
int main()
{
n=get_n();
for(int i=3;i<=n;i++)
points[is_clockwise(1,2,i)].push_back(i);
//cout<<"---"<<endl;
sort(points[0].begin(),points[0].end(),cmp);
//cout<<"---"<<endl;
sort(points[1].begin(),points[1].end(),cmp);
/*
cout<<"0: ";for(auto k:points[0])cout<<k<<" ";cout<<endl;
cout<<"1: ";for(auto k:points[1])cout<<k<<" ";cout<<endl;
*/
hulls[0].push(2);
for(auto k:points[0])
{
while(hulls[0].size()>=2)
{
int tp=hulls[0].top();
hulls[0].pop();
int prv=hulls[0].top();
if(is_clockwise(prv,tp,k)==0)
{
hulls[0].push(tp);
break;
}
}
hulls[0].push(k);
}
hulls[1].push(1);
for(auto k:points[1])
{
while(hulls[1].size()>=2)
{
int tp=hulls[1].top();
hulls[1].pop();
int prv=hulls[1].top();
if(is_clockwise(prv,tp,k)==0)
{
hulls[1].push(tp);
break;
}
}
hulls[1].push(k);
}
for(int w=0;w<2;w++)
{
points[w]={};
while(hulls[w].size())
{
points[w].push_back(hulls[w].top());
hulls[w].pop();
}
}
while(pop_wrong());
give_answer(points[0].size()+points[1].size());
/*
for(auto k:points[0])cout<<k<<" ";cout<<endl;
for(auto k:points[1])cout<<k<<" ";cout<<endl;
*/
return 0;
}
