#include <bits/stdc++.h>
#include "trilib.h"
using namespace std;
#define sz(x) ((int)size(x))
#define all(x) begin(x), end(x)
#define trace(x) cout << #x << ": " << (x) << endl;
typedef long long ll;
mt19937 rnd(chrono::steady_clock::now().time_since_epoch().count());
int rand(int l, int r) { return (int) ((ll) rnd() % (r - l + 1)) + l; }
const int N = 40000;
const ll infL = 3e18;
int n;
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
n = get_n();
vector<int> ord(n);
iota(all(ord), 0);
stable_sort(1 + all(ord), [](int i, int j) {
return !is_clockwise(1, i + 1, j + 1);
});
vector<int> st;
for (int i : ord) {
while (sz(st) > 1 && is_clockwise(st.end()[-2] + 1, st.back() + 1, i + 1)) {
st.pop_back();
}
st.push_back(i);
}
rotate(begin(st), begin(st) + sz(st) - 2, end(st));
ord = st;
st.clear();
for (int i : ord) {
while (sz(st) > 1 && is_clockwise(st.end()[-2] + 1, st.back() + 1, i + 1)) {
st.pop_back();
}
st.push_back(i);
}
give_answer(sz(st));
return 0;
}
