AT_abc435_a [ABC435A] Triangular Number
Description
You are given a positive integer $ N $ .
Output the sum of all integers from $ 1 $ to $ N $ , that is, $ 1+2+\cdots+N $ .
Input Format
The input is given from Standard Input in the following format:
> $ N $
Output Format
Output the sum of all integers from $ 1 $ to $ N $ .
Explanation/Hint
### Sample Explanation 1
Since $ 1+2+3+4+5=15 $ , output $ 15 $ .
### Constraints
- $ 1 \leq N \leq 100 $
- $ N $ is an integer.