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

int main() {
	int a, b = 0;
	cin >> a;
	for (int i = 1; i <= a; i++) {
		b = b + i;
	}
	cout << b;
	return 0;
}



 

#include <bits/stdc++.h>
using namespace std;
int main() {
int n;
cin >> n;
cout <<n*(n+1)/2<< endl;
    return 0;
}