import java.util.Scanner;

public class Solution {

	public static void main(String[] args) {
		Scanner s=new Scanner(System.in);
		int[] height = new int[26];
		for(int i=0;i<26;i++){
			height[i]= s.nextInt();
		}
		char[] str = s.next().toCharArray();
		int count=0,max=0;
		for(char c:str){
			count++;
			int x=c-'a';
			max= Math.max(max, height[x]);
		}
		int ans=max*count;
		System.out.println(ans);
	}

}