#include<algorithm>
#include<complex>
#include<ctype.h>
#include<iomanip>
#include<iostream>
#include<fstream>
#include<map>
#include<math.h>
#include<numeric>
#include<queue>
#include<set>
#include<stack>
#include<stdio.h>
#include<string>
#include<string>
#include<vector>

using namespace std;
typedef long long ll;

#define FOR(i,a,b) for(ll i=(a);i<(b);++i)
#define ALL(v) (v).begin(), (v).end()
#define p(s) cout<<(s)<<endl
#define p2(s, t) cout << (s) << " " << (t) << endl
#define br() p("")
#define pn(s) cout << (#s) << " " << (s) << endl
#define p_yes() p("Yes")
#define p_no() p("No")

const ll mod = 1e9 + 7;
const ll inf = 1e18;

ll f(ll L){
    if(L<3){
        return 0;
    }

    if(L==3){
        return 1;
    }

    ll n = (L - 3)/2 + 1;
    ll sum = n * (n+1) / 2;
    return sum;
}

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);

    // input
    ll L;
    cin >> L;

    ll a = f(L);
    ll b = f(L-2);
    
    p(a+b);

    return 0;
}