#include <atcoder/all>
using namespace atcoder;
#include <bits/stdc++.h>
#define all(a) (a.begin()),(a.end())
#define rall(a) (a.rbegin()),(a.rend())
using namespace std;
using ll=long long;
using ld=long double;
using pll=pair<ll,ll>;
template<class T>bool chmax(T &a, const T &b) {if(a<b) {a=b; return 1;} return 0;}
template<class T>bool chmin(T &a, const T &b) {if(b<a) {a=b; return 1;} return 0;}
istream& operator >> (istream& is, modint1000000007& x) { unsigned int t; is >> t; x=t; return is; }
istream& operator >> (istream& is, modint998244353& x) { unsigned int t; is >> t; x=t; return is; }
istream& operator >> (istream& is, modint& x) { unsigned int t; is >> t; x=t; return is; }
ostream& operator << (ostream& os, const modint1000000007& x) { os << x.val(); return os; }
ostream& operator << (ostream& os, const modint998244353& x) { os << x.val(); return os; }
ostream& operator << (ostream& os, const modint& x) { os << x.val(); return os; }
template<class T1, class T2>istream& operator >> (istream& is, pair<T1,T2>& p) { is >> p.first >> p.second; return is; }
template<class T1, class T2>ostream& operator << (ostream& os, const pair<T1,T2>& p) { os << p.first << " " << p.second; return os;}
template<class T>istream& operator >> (istream& is, vector<T>& v) { for(T& x:v) is >> x; return is; }
template<class T>ostream& operator << (ostream& os, const vector<T>& v) {for(int i=0;i<(int)v.size();i++) {os << v[i] << (i+1 == v.size() ? "":" ");} return os;}
template<class... A> void pt()      { std::cout << "\n"; }
template<class... A> void pt_rest() { std::cout << "\n"; }
template<class T, class... A> void pt_rest(const T& first, const A&... rest) { std::cout << " " << first; pt_rest(rest...); }
template<class T, class... A> void pt(const T& first, const A&... rest)      { std::cout << first; pt_rest(rest...); }
template<typename V, typename H> void resize(vector<V>& vec, const H head){ vec.resize(head); }
template<typename V, typename H, typename ... T> void resize(vector<V>& vec, const H& head, const T ... tail){ vec.resize(head); for(auto& v: vec) resize(v, tail...); }
template<typename V, typename T> void fill(V& x, const T& val){ x = val; }
template<typename V, typename T> void fill(vector<V>& vec, const T& val){ for(auto& v: vec) fill(v, val); }
template<typename H> void vin(istream& is, const int idx, vector<H>& head){ is >> head[idx]; }
template<typename H, typename ... T> void vin(istream& is, const int idx, vector<H>& head, T& ... tail){ vin(is >> head[idx], idx, tail...); }
template<typename H, typename ... T> void vin(istream& is, vector<H>& head, T& ... tail){ for(int i=0; i<(int)head.size(); i++) vin(is, i, head, tail...); }
template<typename H, typename ... T> void vin(vector<H>& head, T& ... tail){ vin(cin, head, tail...); }
map<ll,ll>divisor(ll n){map<ll,ll>res;for(ll i=1;i*i<=n;i++)if(n%i==0){res[i]++;res[n/i]++;}return res;}
map<ll,ll>factrization(ll n){map<ll,ll>res;for(ll i=2;i*i<=n;i++)while(n%i==0){res[i]++;n/=i;}if(n>1)res[n]++;return res;}
static const ll inf=1e18+7;
static const ld pi=acos(-1);
static const ld eps=1e-10;
using v1=vector<ll>;
using v2=vector<v1>;
using v3=vector<v2>;
using v4=vector<v3>;
using S=ll;
S op(S a,S b){return a+b;}
S e(){return 0;}

int main(void) {
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  
  ll N;cin>>N;
  ll K=(N+1)/2;
  pt(K*(K+1)/2);
}