#include "bits/stdc++.h"
#include "trilib.h"
using namespace std;
#define sz(v) ((int)v.size())
#define pb push_back
#define chk is_clockwise
#define indx(j) ((j + sz(ch)) % sz(ch))
void rem(vector<int> &c, int i) {
for (int j = i+1; j < sz(c); ++j)
c[j-1] = c[j];
c.pop_back();
}
void ins(vector<int> &c, int i, int x) {
c.pb(0);
for (int j = sz(c) -1; j >i; --j)
c[j] = c[j-1];
c[i] = x;
}
int main() {
int n = get_n();
vector<int> ch = {1, 2, 3};
if (!chk(1,2,3))
swap(ch[1], ch[2]);
for (int j = 4; j <= n; ++j) {
int l = 1, r = sz(ch);
assert(sz(ch) >=3);
while (l < r) {
int m = (l+r)/2;
if (chk(ch[0], j, ch[m]))
r = m;
else
l = m+1;
}
if (l > 1 && l != sz(ch)) {
if (chk(ch[0], ch[l-1], j) && chk(ch[l-1], ch[l], j) && chk(ch[l], ch[0], j))
continue;
}
ins(ch, l, j);
while (chk(ch[indx(l-2)], ch[l], ch[indx(l-1)])) {
int u = indx(l-1);
rem(ch, u);
if (u < l) --l;
}
while (chk(ch[indx(l+1)], ch[l], ch[indx(l+2)])) {
int u = indx(l+1);
rem(ch, u);
if (u < l) --l;
}
}
give_answer(sz(ch));
}
