using System;
using System.Linq;
using System.Collections;
using System.Collections.Generic;

namespace Brown
{
    using static Ex;
    public class Solve
    {
        public static void Main(string[] args)
        {
            new abc149_d();
        }
    }
    public class abc136_d
    {
        public abc136_d()
        {
            var s = Read.ToArray();
            //var s = Read.Select(v => v == 'L' ? -1 : 1).ToArray();
            var arr = new int[s.Length];
        }
    }
    public class abc149_d
    {
        int n, k;
        public abc149_d()
        {
            (n, k) = ReadIntArray().ToTpl2();
            var score = ReadIntArray();
            var t = Read.Select(c =>
            {
                switch (c)
                {
                    case 'r': return 2;
                    case 's': return 0;
                    case 'p': return 1;
                };
                return 0;
            }).ToArray();

            long ans = 0;
            var arr = new int[n];
            for (int i = 0; i < n; i++)
            {
                var c = t[i];
                if (i >= k && (c == arr[i - k]))
                {
                    for (int a = 0; a < 3; a++)
                    {
                        if (a == c) continue;
                        if ((i + k < n) && a == t[i + k]) continue;
                        c = a;
                        break;
                    }
                }
                else
                {
                    ans += score[c];
                }
                arr[i] = c;
            }
            ans.Cw();
        }
    }
    public class abc_
    {
        public abc_()
        {
        }
    }

    public static class Ex
    {
        public static void Cw(this object s) { Console.WriteLine(s); }



        public static bool Mins<T>(ref T a, T b) where T : IComparable<T> { if (a.CompareTo(b) > 0) { a = b; return true; } return false; }
        public static bool Maxs<T>(ref T a, T b) where T : IComparable<T> { if (a.CompareTo(b) < 0) { a = b; return true; } return false; }
        public static void Swap<T>(ref T a, ref T b) { var t = b; b = a; a = t; }
        public static void Swap<T>(List<T> list, int i, int j) { T tmp = list[j]; list[j] = list[i]; list[i] = tmp; }

        public static long Lcm(int x, int y) { return x / Gcd(x, y) * y; }
        public static long Gcd(long m, long n) { if (n == 0) return m; return Gcd(n, m % n); }
        public static List<string> FastSort(this List<string> s) { s.Sort(StringComparer.Ordinal); return s.ToList(); }
        public static void yesno(this bool b) { (b ? "yes" : "no").Cw(); }
        public static void YesNo(this bool b) { (b ? "Yes" : "No").Cw(); }
        public static void YESNO(this bool b) { (b ? "YES" : "NO").Cw(); }

        public static string Read { get { return Console.ReadLine().Trim(); } }
        public static int ReadInt { get { return int.Parse(Read); } }
        public static long ReadLong { get { return long.Parse(Read); } }
        public static double ReadDouble { get { return double.Parse(Read); } }
        public static string[] ReadArray() { return Read.Split(' '); }
        public static int[] ReadIntArray() { return Read.Split(' ').Select(int.Parse).ToArray(); }
        public static long[] ReadLongArray() { return Read.Split(' ').Select(long.Parse).ToArray(); }
        public static string[] ReadArray(long N) { var v = new string[N]; for (long i = 0; i < N; ++i) v[i] = Read; return v; }
        public static int[] ReadIntArray(long N) { var v = new int[N]; for (long i = 0; i < N; ++i) v[i] = ReadInt; return v; }
        public static long[] ReadLongArray(long N) { var v = new long[N]; for (long i = 0; i < N; ++i) v[i] = ReadLong; return v; }

        public static (T, T) ToTpl2<T>(this T[] v) { return (v[0], v[1]); }
        public static (T, T, T) ToTpl3<T>(this T[] v) { return (v[0], v[1], v[2]); }
        public static (T, T, T, T) ToTpl4<T>(this T[] v) { return (v[0], v[1], v[2], v[3]); }
        public static (T, T, T, T, T) ToTpl5<T>(this T[] v) { return (v[0], v[1], v[2], v[3], v[4]); }


    }
}

Measured memory_bytes: 29996