#include<iostream>
#include<iomanip>
#include<cstdio>
#include<cmath>
#include<string>
#include<cstring>
using namespace std;
int main()
{
	int n,sum=0,i=1;
	while(cin>>n)
	{
		i<=n;
		sum+=i;
		i++;
		cout<<sum<<endl;
	}
	return 0;
}