Score : 500 points
There are N squares numbered 1 to N from left to right. Each square has a character written on it, and Square i has a letter s_i. Besides, there is initially one golem on each square.
Snuke cast Q spells to move the golems.
The i-th spell consisted of two characters t_i and d_i, where d_i is L
or R
.
When Snuke cast this spell, for each square with the character t_i, all golems on that square moved to the square adjacent to the left if d_i is L
, and moved to the square adjacent to the right if d_i is R
.
However, when a golem tried to move left from Square 1 or move right from Square N, it disappeared.
Find the number of golems remaining after Snuke cast the Q spells.
L
or R
.Input is given from Standard Input in the following format:
N Q s t_1 d_1 \vdots t_{Q} d_Q
Print the answer.
3 4 ABC A L B L B R A R
2
8 3 AABCBDBA A L B R A R
5
10 15 SNCZWRCEWB B R R R E R W R Z L S R Q L W L B R C L A L N L E R Z L S L
3