#include<bits/stdc++.h>
#define ll long long
using namespace std;


int main(){
    ll n,s=0;
    cin>>n;
    for (int i=1;i<=n;i++){
        s+=i;
    }
    //meothinhle
    cout<<s;
    return 0;
}

#include <iostream>
using namespace std;
unsigned long long n, to; 
int main() 
{
    cin >> n;
    for(int i = 1; i <= n; i++)
        to += i;
    cout << to;
    return 0;
/*
khanhtaon（*＾-＾*）
*/
}

$#khanhtaon$