N, Q = map(int, input().split())
s = str(input())

t = []
d = []

for _ in range(Q):
    ti, di = map(str, input().split())
    t.append(ti)
    d.append(di)
    
LEFT_DIE = -1
RIGHT_DIE = len(s)

def is_dead(i):
    for ti, di in zip(t, d):
        if s[i] == ti:
            if di == 'L':
                i -= 1
            if di == 'R':
                i += 1
            if i == LEFT_DIE:
                return LEFT_DIE
            if i == RIGHT_DIE:
                return RIGHT_DIE
    return 0

low = -1
high = len(s);
# LEFT
while high - low > 1:
    mid = (low + high) // 2;
    if is_dead(mid) == LEFT_DIE:
        low = mid
    else:
        high = mid
left_edge = high

low = -1
high = len(s);
# RIGHT
while high - low > 1:
    mid = (low + high) // 2;
    if is_dead(mid) == RIGHT_DIE:
        high = mid
    else:
        low = mid
right_edge = low

#print(left_edge, right_edge)
ans_s = s[left_edge:right_edge+1]
#print(ans_s)
ans = len(ans_s)
print(ans)

        
        
        
        
        
        