#include<iostream>
using namespace std;
int main(){
int n;
int a,hap = 0;
cin >> n;
for ( int i=1; i<=n; i++){
hap += i;
}
cout << hap << endl;
return 0;
}
#include<iostream>
using namespace std;
int main(){
int n;
int a,hap = 0;
cin >> n;
for ( int i=1; i<=n; i++){
hap += i;
}
cout << hap << endl;
return 0;
}