#!/usr/bin/env python3

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

instructions = tuple(int(char == "R") for char in next(lines))
next(lines)
nodes = {line[:3]: (line[7:10], line[12:15]) for line in lines}

node = "AAA"
cnt = 0

while True:
    for char in instructions:
        node = nodes[node][char]
        cnt += 1
        if node == "ZZZ":
            print(cnt)
            exit(0)