#include <bits/stdc++.h>
#include "trilib.h"
#define ff first
#define ss second
#define ll long long
using namespace std;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
int n;
int res = 1;
int main() {
n = get_n();
int v1 = rng() % n + 1, v2 = rng () % n + 1;
while(v1 == v2){
v1 = rng() % n + 1;
v2 = rng() % n + 1;
}
while(true){
int i;
for(i = 1; i <= n; i++){
if(v1 == i || v2 == i) continue;
if(is_clockwise(v1, v2, i) == 0){
if(rng() % 2 == 0)
v1 = i;
else
v2 = i;
break;
}
}
if(i == n + 1) break;
}
int s = v1;
while(v2 != s){
res++;
for(int i = 1; i <= n; i++){
if(i == v1 || i == v2) continue;
if(is_clockwise(v1, v2, i)){
v1 = i;
}
}
swap(v2, v1);
}
give_answer(res);
}
