Even Substrings

0ms

262144K

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.

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 $$$s$$$.

Sample Input:

4
1234

Sample Output:

Sample Input:

4
2244

Sample Output:

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.

Informação

Provedor Codeforces

Código CF1139A