import sys

def main():
    input = sys.stdin.readline
    N, Q = map(int, input().split())
    S = list(map(str, input().strip()))
    order = [tuple(map(str, input().split())) for _ in range(Q)]
    order = order[::-1]

    left, right = 0, N-1
    for a in order:
        t, d = a[0], a[1]

        if d == 'L':
            if S[left] == t:
                left += 1
                if left > N - 1:
                    return 0

            if right < N - 1 and S[right + 1] == t:
                right = min(N - 1, right + 1)

        else:
            if left > 0 and S[left - 1] == t:
                left = max(0, left - 1)

            if S[right] == t:
                right -= 1
                if right < 0:
                    return 0

    return right - left + 1


if __name__ == '__main__':
    print(main())
