Problems
Recursion - 1
Recursion - 1
Implement the recursive function:
$$
f(n) = \begin{cases}
0, n = 0\\
f(n - 1) + n, n > 0
\end{cases}
$$
\InputFile
One integer $n~(0 \le n \le 1000)$.
\OutputFile
Print the value of $f(n)$.
Input example #1
5
Output example #1
15