Brutality
Contest: Educational Codeforces Round 59 (Rated for Div. 2)
Difficulty rating: 1300
Tags: greedy, sortings, two pointers

You are playing a new famous fighting game: Kortal Mombat XII. You have to perform a brutality on your opponent's character.

You are playing the game on the new generation console so your gamepad have $$$26$$$ buttons. Each button has a single lowercase Latin letter from 'a' to 'z' written on it. All the letters on buttons are pairwise distinct.

You are given a sequence of hits, the $$$i$$$-th hit deals $$$a_i$$$ units of damage to the opponent's character. To perform the $$$i$$$-th hit you have to press the button $$$s_i$$$ on your gamepad. Hits are numbered from $$$1$$$ to $$$n$$$.

You know that if you press some button more than $$$k$$$ times in a row then it'll break. You cherish your gamepad and don't want to break any of its buttons.

To perform a brutality you have to land some of the hits of the given sequence. You are allowed to skip any of them, however changing the initial order of the sequence is prohibited. The total damage dealt is the sum of $$$a_i$$$ over all $$$i$$$ for the hits which weren't skipped.

Note that if you skip the hit then the counter of consecutive presses the button won't reset.

Your task is to skip some hits to deal the maximum possible total damage to the opponent's character and not break your gamepad buttons.

Input format:
The first line of the input contains two integers $$$n$$$ and $$$k$$$ ($$$1 \le k \le n \le 2 \cdot 10^5$$$) — the number of hits and the maximum number of times you can push the same button in a row.

The second line of the input contains $$$n$$$ integers $$$a_1, a_2, \dots, a_n$$$ ($$$1 \le a_i \le 10^9$$$), where $$$a_i$$$ is the damage of the $$$i$$$-th hit.

The third line of the input contains the string $$$s$$$ consisting of exactly $$$n$$$ lowercase Latin letters — the sequence of hits (each character is the letter on the button you need to press to perform the corresponding hit).

Output format:
Print one integer $$$dmg$$$ — the maximum possible damage to the opponent's character you can deal without breaking your gamepad buttons.

Constraints:
Time limit: 1.0 s
Memory limit: 256.0 MB

Note:
In the first example you can choose hits with numbers $$$[1, 3, 4, 5, 6, 7]$$$ with the total damage $$$1 + 16 + 18 + 7 + 2 + 10 = 54$$$.

In the second example you can choose all hits so the total damage is $$$2 + 4 + 1 + 3 + 1000 = 1010$$$.

In the third example you can choose all hits expect the third one so the total damage is $$$2 + 4 + 3 + 1000 = 1009$$$.

In the fourth example you can choose hits with numbers $$$[2, 3, 6, 8]$$$. Only this way you can reach the maximum total damage $$$15 + 2 + 8 + 16 = 41$$$.

In the fifth example you can choose only hits with numbers $$$[2, 4, 6]$$$ with the total damage $$$18 + 19 + 15 = 52$$$.

In the sixth example you can change either first hit or the second hit (it does not matter) with the total damage $$$10$$$.

Example input:
7 3
1 5 16 18 7 2 10
baaaaca

Example output:
54

Example input:
5 5
2 4 1 3 1000
aaaaa

Example output:
1010

Editorial:
All you need in this problem is two simple technique: two pointers and sorting. Let's consider maximum by inclusion segments of equal letters in the initial string. Let the current segment be $$$[l; r]$$$ and its length is $$$len = r - l + 1$$$. If $$$len < k$$$ then we can press all buttons and deal all damage corresponding to them. Otherwise it is obviously more profitable to press $$$k$$$ best (by damage) buttons. So let's create the array $$$val$$$, push all values $$$a_i$$$ such that $$$l \le i \le r$$$ in this array, sort them, take $$$min(|val|, k)$$$ best by damage ($$$|val|$$$ is the size of the array $$$val$$$) and go to the next segment.