#302. Loop: 1+2+...+n
You get a positive integer n. Use a `for` loop to find **1+2+...+n**.
### Input
One integer n (1 ≤ n ≤ 20).
### Output
One integer.
Examples
Input
6
Output
21
Input
3
Output
6
💡 You can solve it with Python, JavaScript or blocks. Read the input line by line with input(). Don't print a question (like input("Number: ")). Print exactly what the output asks for, nothing more.