A12369 | Even Substrings

You are given a string $s=s_1s_2\dots s_n$ of length $n$ , which only contains digits $1$ , $2$ , ..., $9$ .

A substring $s[l \dots r]$ of $s$ is a string $s_l s_{l + 1} s_{l + 2} \ldots s_r$ . A substring $s[l \dots r]$ of $s$ is called even if the number represented by it is even.

Find the number of even substrings of $s$ . Note, that even if some substrings are equal as strings, but have different $l$ and $r$ , they are counted as different substrings.

The first line contains an integer $n$ ( $1 \le n \le 65000$ ) — the length of the string $s$ .

The second line contains a string $s$ of length $n$ . The string $s$ consists only of digits $1$ , $2$ , ..., $9$ .

Print the number of even substrings of $s$ .