View Code of Problem 30

#include<iostream>
#include<vector>
#include<algorithm>
#include<iomanip>
#include<string>
#include<cmath>

using namespace std;

int main()
{
	int n;
	while (cin >> n) {

		vector<int> dp(n + 1);
		dp[1] = 1;

		for (int i = 1; i <= n; i++)
			dp[i] = i + dp[i - 1];

		cout << dp[n] << endl;
	}
}