#include<bits/stdc++.h>
using namespace std;
#define MOD 1000000007
 
int main() {
  int N,Q;
  cin >> N >> Q;
  string s;
  cin >> s;
  vector<string> t(Q);
  vector<string> d(Q);
  for(int i=0;i<Q;i++){
    cin >> t[i] >> d[i];
  }
  
  int pos_l=0;
  int pos_r=N-1;
  for(int i=Q-1;i>=0;i--){
    if(d[i]=="R"){
      if(pos_l-1>=0){
        if(s[pos_l-1]==t[i][0])
          pos_l--;
      }
      if(s[pos_r]==t[i][0])
        pos_r--;
    }else{
      if(pos_r+1<N){
        if(s[pos_r+1]==t[i][0])
          pos_r++;
      }
      if(s[pos_l]==t[i][0])
        pos_l++;
    }
  }
  
  
  cout<<pos_r-pos_l+1<<endl;
  return 0;
}