Triangular Number

Time Limit: 1 sec

**The Problem**

A **triangular number** or **triangle number** counts the objects that can form an equilateral triangle, as in the diagram on the below. The ** n**th triangular number is the number of dots composing a triangle with

*n*dots on a side.

Simply, Triangular numbers are numbers that create triangle.

So,

1st triangular number is 1

2nd triangular number is 3

3rd triangular number is 6

and so on....

Make a simple program that reads one variable named **n**. Calculate and print the **n**th triangular number.

**The Input**

Input file contain a series of line, each line contain 1 integer number **n**** **(0<**n**<100000000). Input is terminated by **EOF**.

**The Output**

For each line of input, output will be the **n**th triangular number in a seperate line.

**Sample Input**

1

4

2

**Sample Output**

1

10

3

Problem Setter: Shahin ShamS