#!/usr/bin/env lua
require("ext")
local sacks = {}
local common = {}
for line in io.lines() do
	local compart_1 = {}
	for i = 1,(#line/2) do
		compart_1[line:sub(i,i)] = true
	end
	for i = (#line/2+1), #line do
		local sb = line:sub(i,i)
		if compart_1[sb] then
			table.insert(common,sb)
			break
		end
	end
end
local sum = 0
for _, p in pairs(common) do
	if p >= 'a' and p <= 'z' then
		sum = sum + (p:byte() - ('a'):byte() + 1)
	elseif p >= 'A' and p <= 'Z' then
		sum = sum + (p:byte() - ('A'):byte() + 1) + 26
	end
end
print(sum)