import sys
from collections import deque
import copy
import math
def get_read_func(fileobject):
    if fileobject == None :
        return raw_input
    else:
        return fileobject.readline

def is_fall(S, start, end_point, magic_list):
    i = start
    for ml in magic_list:
        if i == -1 or i == len(S):
            break
        if S[i] == ml[0]:
            if ml[1] == 'L':
                i -= 1
            else:
                i += 1
        if i == end_point:
            return True
    return False




def bin_search(S,  magic_list, end_point):
    L = -1
    R = len(S)
    while 1:
        if R - L <= 1:
            if end_point == len(S):
                return R
            else:
                return L
        M = (L + R)/2
        res = is_fall(S, M, end_point, magic_list)
        if res == True:
            if end_point == len(S):
                R = M
            else:
                L = M
        else:
            if end_point == len(S):
                L = M
            else:
                R = M





def main():
    if len(sys.argv) > 1:
        f = open(sys.argv[1])
    else:
        f = None
    read_func = get_read_func(f);
    input_raw = read_func().strip().split()
    [N, Q] = [int(input_raw[0]), int(input_raw[1])]
    input_raw = read_func().strip().split()
    S = input_raw[0]

    magic_list = []
    for i in range(Q):
        input_raw = read_func().strip().split()
        [t, s] = [(input_raw[0]), (input_raw[1])]
        magic_list.append((t, s))
    L_end = bin_search(S, magic_list, -1) + 1
    R_end = N - bin_search(S, magic_list, len(S))
    print N - L_end - R_end




if __name__ == '__main__':
    main()
