Problem Statement

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.

Input

Input is given from Standard Input in the following format:
N Q
s
t_1 d_1
$\vdots$
t_{Q} d_Q

Output

Print the answer.

Constraints

• $1 \leq N,Q \leq 2 \times 10^{5}$
• |s| = N
• s_i and t_i are uppercase English letters.
• d_i is L or R.

Sample Input 1

3 4
ABC
A L
B L
B R
A R

Sample Output 1

2

• Initially, there is one golem on each square.
• In the first spell, the golem on Square 1 tries to move left and disappears.
• In the second spell, the golem on Square 2 moves left.
• In the third spell, no golem moves.
• In the fourth spell, the golem on Square 1 moves right.
• After the four spells are cast, there is one golem on Square 2 and one golem on Square 3, for a total of two golems remaining.

Sample Input 2

8 3
AABCBDBA
A L
B R
A R

Sample Output 2

5

• After the three spells are cast, there is one golem on Square 2, two golems on Square 4 and two golems on Square 6, for a total of five golems remaining.
• Note that a single spell may move multiple golems.

Sample Input 3

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

Sample Output 3

3

见题面 Input 部分

见题面 Output 部分