// ~Be name khoda~ //
#include<bits/stdc++.h>
#include "trilib.h"
using namespace std;
typedef long long ll;
#define pb push_back
#define mp make_pair
#define all(x) x.begin(), x.end()
#define fi first
#define se second
#define cl clear
#define endll '\n'
const int maxn = 1e6 + 10;
const int maxn5 = 5e5 + 10;
const int maxnt = 1.2e6 + 10;
const int maxn3 = 1e3 + 10;
const int mod = 1e9 + 7;
const ll inf = 2e18;
int nxt[maxn5], pre[maxn5], av[maxn5];
int main()
{
ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
int n = get_n();
nxt[1] = 2; nxt[2] = 3; nxt[3] = 1;
pre[1] = 3; pre[2] = 1; pre[3] = 2;
if(n == 3){
give_answer(3);
return 0;
}
int st = 1;
for(int i = 4; i <= n; i++){
int out = -1;
bool hullorder = is_clockwise(st, nxt[st], nxt[nxt[st]]);
bool ans = is_clockwise(st, nxt[st], i);
ans ^= hullorder;
if(ans){
out = st;
}
else{
int have = nxt[st];
int hi = 0;
for(int i = 0; have != st; i++, have = nxt[have]){
av[i] = have;
hi = i;
}
int sz = hi;
int lo = 0;
while(hi - lo > 1){
int mid = (lo + hi) >> 1;
if(hullorder ^ is_clockwise(st, av[mid], i))
hi = mid;
else
lo = mid;
}
//cout << "here " << st << ' ' << sz << ' ' << lo << ' ' << hi << endl;
if(hi == sz && is_clockwise(st, pre[st], nxt[st]) != is_clockwise(st, pre[st], i)){
lo = hi;
//cout << "oh spc case " << endl;
if(is_clockwise(av[lo], st, nxt[st]) != is_clockwise(av[lo], st, i))
out = av[lo];
}
else{
if(is_clockwise(av[lo], av[lo + 1], nxt[av[lo + 1]]) != is_clockwise(av[lo], av[lo + 1], i))
out = av[lo];
}
}
if(out == -1)
continue;
//cout << "it's " << out << endl;
for(out = nxt[out]; ; out = nxt[out])
if(is_clockwise(out, nxt[out], nxt[nxt[out]]) == is_clockwise(out, nxt[out], i))
break;
int r = out;
//cout << "hola " << r << endl;
for(out = pre[out]; ; out = pre[out])
if(is_clockwise(out, pre[out], pre[pre[out]]) == is_clockwise(out, pre[out], i))
break;
int l = out;
//cout << "wow it's " << l << endl;
nxt[l] = i;
pre[r] = i;
nxt[i] = r;
pre[i] = l;
st = i;
/*
cout << "let's check " << i << endl;
int j = st;
cout << j << ' ';
j = nxt[j];
while(j != st){
cout << j << ' ';
j = nxt[j];
}
cout << endl;
//*/
}
int num = 1;
for(int i = nxt[st]; i != st; i = nxt[i]) num++;
give_answer(num);
}
