import java.util.Scanner;

public class Solution {

	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		int[] height = new int[26];
		for (int i = 0; i < height.length; i++) {
			height[i] = in.nextInt();
		}
		String word = in.next();
		int length = word.length();
		int maxHeight = 0;
		for (int i = 0; i < word.length(); i++) {
			maxHeight = Math.max(maxHeight, height[word.charAt(i) - 97]);
		}
		System.out.println(maxHeight * length);
		in.close();
	}
}