一、

import os
import sys
def dps(s):
    dp = [0] * len(s)
    dp[0] = ord(s[0]) - 96
    if len(s) == 1:
        return dp[-1]
    dp[1] = max(ord(s[0]) - 96, ord(s[1]) - 96)
    for i in range(2, len(s)):
        dp[i] = max(dp[i - 1], dp[i - 2] + (ord(s[i])) - 96)
    return dp[-1]
s = input()
print(dps(s))