//Author: Fuadul Hasan(fuadul202@gmail.com)
//BSMRSTU,Gopalganj
#include<bits/stdc++.h>
using namespace std;int tc = 1;
#define happy ios::sync_with_stdio(false);
#define coding  cin.tie(0);
#define F first
#define S second
#define mp make_pair
#define ll long long
#define Pi atan(1)*4
#define pb  push_back
#define vpr vector<pr> 
#define pr pair<int, int> 
#define vi std::vector<int>
#define vll std::vector<ll>
#define YES printf("YES\n");
#define NO printf("NO\n");
#define Yes printf("Yes\n");
#define No printf("No\n");
#define all(n) n.begin(),n.end()
#define point(x) setprecision(x)
#define Test printf("Case %d: ",tc++);
#define Unique(c) (c).resize(unique(all(c))-(c).begin())
#define vout(v) for (auto z: v) cout << z << " "; cout << endl;

const int M = 1e9 + 7;
const ll  Inf = (ll)2e18 + 5;
const int N   = 2e5 + 5;
ll vis[N],res[N];

int solve() 
{
	//happy coding

	int n;
	cin>>n;
	cout<<(n*(n+1))/2<<endl;

	
	return 0;
}
int main(){
	int test = 1;
	//scanf("%d", &test);
	while (test--)solve();return 0;
}