public class Sum 
{
	public static void main(String[] args) 
	{
		int[] x = new int [101];
		for (int i = 0; i<x.length; i++ )
			x[i] = i;
		int sum = 0;
		for(int i = 0; i<x.length; i++)
			sum += x[i];
			System.out.println(sum);
	}
}