#include <iostream>
#include <string>
#include <algorithm>
#include <vector>
#include <array>
#include <queue>
#include <deque>
#include <map>
#include <set>
#include <sstream>
#include <stdio.h>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <list>
#include <numeric>
#include <stack>
#include <iomanip>
#include <random>
#include <complex>
#include <functional>

using namespace std;

#define Rep(i,a,b) for(int i = a; i < b; ++i)
#define rep(i,b) Rep(i,0,b)
#define allof(a) (a).begin(), (a).end()

#define Yes(q) ((q) ? "Yes" : "No")
#define YES(q) ((q) ? "YES" : "NO")
#define Possible(q) ((q) ? "Possible" : "Impossible")
#define POSSIBLE(q) ((q) ? "POSSIBLE" : "IMPOSSIBLE")

using ll =  long long;

using pint = std::pair<int, int>;
using pll = std::pair<ll, ll>;


constexpr int inf = 1e9 + 7;
constexpr ll infll = 1ll << 60ll;
constexpr ll mod = 1e9 + 7;
// 0~3までは右左下上 4~7までは斜め
constexpr int dx[] = { 1, 0, -1, 0, 1, 1, -1, -1 };
constexpr int dy[] = { 0, -1, 0, 1, 1, -1, -1, 1 };

namespace { 
	template<typename T> void chmax(T& a, T b) { a = std::max(a, b); }
	template<typename T> void chmin(T& a, T b) { a = std::min(a, b); }
	template<typename T> void chadd(T& a, T b) { a = a + b; }
	template<typename T> T gcd(T a, T b) { if (a < b) std::swap(a, b); while (b) std::swap(a %= b, b); return a; }
	template<typename T> T lcm(const T a, const T b) { return a / gcd(a, b) * b; }

	template <typename T> void Cout(T& x, char end = '\n') { std::cout << x << end; }
	template <typename T> void Cout(std::vector<T>& x, char sep = ' ', char end = '\n') { for (std::size_t i = 0, sz = x.size(); i < sz; i++) { std::cout << x[i] << (i == sz - 1 ? end : sep); } }


	// 標準入出力
	struct inp {
		size_t sz;
		inp(size_t _sz = 1) : sz(_sz) {}
		template <typename T> operator T () const { T a; std::cin >> a; return a; }
		template <typename T> operator std::vector<T>() const { vector<T> a(sz); for (std::size_t i = 0; i < sz; i++) std::cin >> a[i]; return a; }
		template <typename T, typename U> operator std::pair<T, U>() const { T f; U s; std::cin >> f >> s; return std::pair<T, U>(f, s); }
	};

	inp inp1; // input one

	// T は返り値の型
	template<typename T>
	T BinarySearch(T left, T right, function<bool(T)> Check) {
		while (right - left > 1) {
			int mid = (right + left) / 2;
			if (Check(mid)) left = mid; // 右を探す
			else right = mid;                       // 左を探す
		}
		// mid = left, mid = right - 1 となっている
		return left;
	}
}


int main() {

	int n, q;
	string s;
	cin >> n >> q >> s;
	vector<char> t(q), d(q);
	rep(i, q) cin >> t[i] >> d[i];

	int left_drop = BinarySearch<int>(0, n, [&](int mid)->bool {
		// midが左にドロップするかどうか
		int pos = mid;
		bool drop = false;
		rep(i, q) {
			if (s[pos] != t[i]) continue;
			// 移動する番
			if (d[i] == 'L') --pos;
			else ++pos;

			if (pos < 0) {
				drop = true;
				break;
			}
			if (pos >= n) {
				break;
			}
		}
		return drop;
		});

	int right_drop = BinarySearch<int>(0, n, [&](int mid)->bool {
		// midが右にドロップするかどうか
		int pos = mid;
		bool drop = false;
		rep(i, q) {
			if (s[pos] != t[i]) continue;
			// 移動する番
			if (d[i] == 'L') --pos;
			else ++pos;

			if (pos < 0) {
				//drop = true;
				break;
			}
			if (pos >= n) {
				drop = true;
				break;
			}
		}
		return !drop;
		}) + 1;

	int ans = right_drop - left_drop - 1;
	Cout(ans);

	return 0;
}

Measured memory_bytes: 900