#include <bits/stdc++.h>
#include "trilib.h"
#define rep(i, a, b) for(int i = a; i <= b; i ++)
#define all(x) x.begin(), x.end()
using namespace std;
vector<int> v[2], hull;
void solve() {
int n = get_n();
v[0].push_back(1);
v[1].push_back(2);
rep(i, 3, n) v[is_clockwise(2, 1, i)].push_back(i);
rep(i, 0, 1) sort(v[i].begin() + 1, v[i].end(),
[](int a, int b) { return is_clockwise(1, b, a);});
rep(tp, 0, 1) {
for(auto i : v[tp]) {
while(hull.size() > 1 && is_clockwise(
hull[hull.size() - 1], i, hull[hull.size() - 2])) hull.pop_back();
hull.push_back(i);
}
}
int ft = 0, bk = hull.size() - 1;
while(true) {
bool done = 1;
while(is_clockwise(hull[bk], hull[ft], hull[bk - 1])) {
done = 0, bk--;
}
while(is_clockwise(hull[ft], hull[ft + 1], hull[bk])) {
done = 0, ft++;
}
if(done) break;
}
give_answer(bk - ft + 1);
return;
}
signed main() {
solve();
return 0;
}
