#include <bits/stdc++.h>
using namespace std;
#define endl '\n'
#define IOS ios::sync_with_stdio(0); cin.tie(0); cout.tie(0)
#define pb push_back

#define Yes cout << "Yes\n"
#define No cout << "No\n"
#define YES cout << "YES\n"
#define NO cout << "NO\n"
#define ff first
#define ss second
#define fori(x,y) for(int i=x;i<=(int)(y);++i)
#define forj(x,y) for(int j=x;j<=(int)(y);++j)
#define fork(x,y) for(int k=x;k<=(int)(y);++k)

#define debug(x) cerr << #x << " = " << x << endl

typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;

ll MOD = 998244353;
ll qpow(ll a,ll p) {ll res=1; while(p) {if (p&1) {res=res*a%MOD;} a=a*a%MOD; p>>=1;} return res;}

signed main() {
	IOS;
    
    int n;
    cin >> n;
    ll ans = 0;
    fori(1, 1e8+n) ans = ans+i;
    cout << ans << endl;
	return 0;
}