Score : $100$ points
There are $N$ children in AtCoder Kindergarten. Mr. Evi will arrange the children in a line, then give $1$ candy to the first child in the line, $2$ candies to the second child, ..., $N$ candies to the $N$-th child. How many candies will be necessary in total?
The input is given from Standard Input in the following format:
Print the necessary number of candies in total.
The answer is $1+2+3=6$.
The sum of the integers from $1$ to $10$ is $55$.
Only one child. The answer is $1$ in this case.