#625. Sum at even positions
Find the sum of the elements at positions 2, 4, 6, ... (counting from 1).
### Input
The first line has n, the second line has n integers separated by spaces.
### Output
A number.
Examples
Input
8 33 -15 -18 4 36 -36 -31 -39
Output
-86
Input
6 6 -22 43 1 18 -18
Output
-39
💡 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.