import std.stdio, std.conv, std.functional, std.string;
import std.algorithm, std.array, std.container, std.range, std.typecons;
import std.numeric, std.math, std.random;
import core.bitop;

string FMT_F = "%.10f";

static string[] s_rd;
T RD(T = long)() { while(!s_rd.length) s_rd = readln.chomp.split; string res = s_rd[0]; s_rd.popFront; return res.to!T; }
string RDR()() { return readln.chomp; }
T[] ARR(T = long)(in string str, T fix = 0) { auto r = str.split.to!(T[]); r[] += fix; return r; }
size_t[] MAKE_IDX(alias less = "a < b", Range)(Range range) { auto idx = new size_t[](range.length); makeIndex!(less)(range, idx); return idx;}
size_t MIN_POS(alias less = "a < b", Range)(Range range) { auto r = minPos!(less)(range); return range.length - r.length; }

bool inside(T)(T x, T b, T e) { return x >= b && x < e; }
bool minimize(T)(ref T x, T y) { if (x > y) { x = y; return true; } else { return false; } }
bool maximize(T)(ref T x, T y) { if (x < y) { x = y; return true; } else { return false; } }

long mod = 10^^9 + 7;
void moda(ref long x, long y) { x = (x + y) % mod; }
void mods(ref long x, long y) { x = ((x + mod) - (y % mod)) % mod; }
void modm(ref long x, long y) { x = (x * y) % mod; }

void main()
{
	auto N = RD;
	auto Q = RD;
	auto s = RD!string;
	auto t = new char[](Q);
	auto d = new char[](Q);
	foreach (i; 0..Q)
	{
		t[i] = RD!char;
		d[i] = RD!char;
	}

	long[256] cnt1, cnt2;
	foreach_reverse (i; 0..Q)
	{
		auto num = t[i] - 'A';
		if (d[i] == 'L' && t[i] == s[0])
		{
			++cnt1[t[i]];
			s.popFront;
			if (cnt2[num] != 0)
			{
				--cnt2[num];
				s ~= t[i];
			}
		}
		else if (d[i] == 'R' && t[i] == s[$-1])
		{
			++cnt2[t[i]];
			s.popBack;
			if (cnt1[num] != 0)
			{
				--cnt1[num];
				s = t[i] ~ s;
			}
		}
	}

	writeln(s.length);
	stdout.flush();
	debug readln();
}