#include<bits/stdc++.h>
#define pi 3.141592653589793238
#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx2,bmi2,lzcnt,popcnt")
#define MOD 1000000007
#define INF 999999999999999999 
#define pb push_back
#define ff first
#define ss second
 
#define mt make_tuple
#define printclock cerr<<"Time : "<<1000*(long double)clock()/(long double)CLOCKS_PER_SEC<<"ms\n";
#define ll long long
#define fast ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
using namespace std;
#include <ext/pb_ds/assoc_container.hpp>

using namespace __gnu_pbds;
 
typedef tree<ll, null_type, less<ll>, rb_tree_tag, tree_order_statistics_node_update> indexed_set;
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
ll rand(ll B) { return (unsigned ll)rng() % B;}

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
 
int main() {
    //freopen("input.txt", "r", stdin);
    //freopen("output.txt", "w", stdout);
    fast;
    ll _T = 1;
    
    // cin >> _T;
    while (_T--) {
        ll n;
        cin >> n;
        ll d = (n + 1) / 2;
        ll ans = (d * (2 + (d - 1) * 2)) / 2;
        ans -= (d * (d - 1)) / 2;
        cout << ans << "\n";
    }
    return 0;
}