Even Substrings
Description
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 $s$.
Input
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 $1$, $2$, ..., $9$.
Output
Print the number of even substrings of $s$.
Samples
4
1234
6
4
2244
10
Note
In the first example, the $[l, r]$ pairs corresponding to even substrings are:
- $s[1 \dots 2]$
- $s[2 \dots 2]$
- $s[1 \dots 4]$
- $s[2 \dots 4]$
- $s[3 \dots 4]$
- $s[4 \dots 4]$
In the second example, all $10$ substrings of $s$ are even substrings. Note, that while substrings $s[1 \dots 1]$ and $s[2 \dots 2]$ both define the substring "2", they are still counted as different substrings.