#include<iostream>
using namespace std;
int main() {
int a;
int b;
int n=0;
cin >> b;
for (int i = 1; i <=b; i++) {
a = i;
n+=a;
}
cout << n << endl;
system("pause");
#include<iostream>
using namespace std;
int main() {
int a;
int b;
int n=0;
cin >> b;
for (int i = 1; i <=b; i++) {
a = i;
n+=a;
}
cout << n << endl;
system("pause");
}