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

class EOFException : Throwable { this() { super("EOF"); } }
string[] tokens;
string readToken() { for (; tokens.empty; ) { if (stdin.eof) { throw new EOFException; } tokens = readln.split; } auto token = tokens.front; tokens.popFront; return token; }
int readInt() { return readToken.to!int; }
long readLong() { return readToken.to!long; }
real readReal() { return readToken.to!real; }

bool chmin(T)(ref T t, in T f) { if (t > f) { t = f; return true; } else { return false; } }
bool chmax(T)(ref T t, in T f) { if (t < f) { t = f; return true; } else { return false; } }

int binarySearch(alias pred, T)(in T[] as) { int lo = -1, hi = cast(int)(as.length); for (; lo + 1 < hi; ) { const mid = (lo + hi) >> 1; (unaryFun!pred(as[mid]) ? hi : lo) = mid; } return hi; }
int lowerBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a >= val)); }
int upperBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a > val)); }


enum L = 26;

int N, Q;
string S;
char[] T, D;

int calc(int x) {
  foreach (q; 0 .. Q) {
    if (S[x] == T[q]) {
      x += ((D[q] == 'L') ? -1 : +1);
      if (!(0 <= x && x < N)) {
        return x;
      }
    }
  }
  return x;
}

void main() {
  try {
    for (; ; ) {
      N = readInt();
      Q = readInt();
      S = readToken();
      T = new char[Q];
      D = new char[Q];
      foreach (q; 0 .. Q) {
        T[q] = readToken()[0];
        D[q] = readToken()[0];
      }
      
      debug {
        foreach (x; 0 .. N) {
          writeln("calc ", x, " = ", calc(x));
        }
      }
      int ansL, ansR;
      {
        int lo = -1, hi = N;
        for (; lo + 1 < hi; ) {
          const mid = (lo + hi) / 2;
          ((calc(mid) >= 0) ? hi : lo) = mid;
        }
        ansL = hi;
      }
      {
        int lo = -1, hi = N;
        for (; lo + 1 < hi; ) {
          const mid = (lo + hi) / 2;
          ((calc(mid) < N) ? lo : hi) = mid;
        }
        ansR = lo;
      }
      int ans = ansR - ansL + 1;
      chmax(ans, 0);
      writeln(ans);
    }
  } catch (EOFException e) {
  }
}
