```go
package main

import (
	"fmt"
	"sort"
)

func main() {
	var n, k int
	fmt.Scan(&n, &k)
	a := make([]int64, n)
	for i := 0; i < n; i++ {
		fmt.Scan(&a[i])
	}
	var s string
	fmt.Scan(&s)
	var total int64 = 0
	for i := 0; i < n; {
		j := i
		var group []int64
		char := s[i]
		for ; j < n && s[j] == char; j++ {
			group = append(group, a[j])
		}
		l := len(group)
		if l <= k {
			for _, v := range group {
				total += v
			}
		} else {
			sort.Slice(group, func(x, y int) bool {
				return group[x] < group[y]
			})
			for t := l - k; t < l; t++ {
				total += group[t]
			}
		}
		i = j
	}
	fmt.Println(total)
}
```