import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
String str = scanner.next();
int n = str.length();
int[][] f = new int[n + 1][2];
f[1][1] = str.charAt(0) - 'a' + 1;
for (int i = 2; i <= n; i++) {
f[i][0] = Math.max(f[i - 1][0], f[i - 1][1]); // 不选
f[i][1] = f[i - 1][0] + str.charAt(i - 1) - 'a' + 1; // 选
}
System.out.println(Math.max(f[n][0], f[n][1]));
}
}