ABC_43 - A - キャンディーとN人の子供イージー / Children and Candies

#include <bits/stdc++.h>

#define forn(l, r) for(int i = l; i < (r); ++i)
#define forj(l, r) for(int j = l; j < (r); ++j)
#define TAM 1000100
#define SYNC ios::sync_with_stdio(0);
#define $ << ' ' <<
#define F first
#define S second
#define endl '\n'


using namespace std;

using ll = long long int;
using ii = pair<int, int>;
using vii = vector<ii>;
using vi = vector<int>;
using graph = vector<vi>;
const int INF = 0x3f3f3f3f;
const int MAXN = 112345;
const ll mod = 1000000007;

int main() {
    //SYNC
    int n;
    cin >> n;
    int ans = 0;
    for (int i = 1; i <= n; i++) {
        ans += i;
    }
    cout << ans << endl;
    return 0;
}