#!/usr/bin/env python3
import re
from collections import Counter, defaultdict

lines = (x.strip() for x in open("input.txt"))
first = next(lines)
next(lines)

combinations = Counter(first[a:a+2] for a in range(len(first)-1))
replacements = defaultdict(list)

for line in lines:
    (a, b), insert = re.match(r"([A-Z]{2}) -> ([A-Z])", line).groups()
    replacements[a+insert].append(a+b)
    replacements[insert+b].append(a+b)

for _ in range(40):
    combinations = {
        k: sum_val for k, v in replacements.items() if (sum_val := sum(combinations.get(x, 0) for x in v)) > 0
    }

letters = Counter(first[0] + first[-1])
for key, cnt in combinations.items():
    letters[key[0]] = letters.get(key[0], 0) + cnt
    letters[key[1]] = letters.get(key[1], 0) + cnt

print((max(letters.values()) - min(letters.values())) // 2)