#include <bits/stdc++.h>
using namespace std;

int main() {
int N;
  int Q;
  cin >> N >> Q;
  int ans=N;
  vector<int> vec(N);
    string S;
   cin >> S;

  for(int i=0; i<N; i++){
    vec.at(i) = 1 ;
  }
  
 for(int i=0; i<Q; i++){
   char ti;
   char di;
   cin >> ti >> di;
     if( (S.at(0) == ti) & (di == 'L')){
       ans = ans - vec.at(0);
         vec.at(0) = 0;
     }
     if( (S.at(0) == ti) & (di == 'R')){
         vec.at(1) = ( vec.at(1) + vec.at(0) );
       vec.at(0) = 0;
     }
     if( (S.at(N - 1) == ti) & (di == 'R')){
       ans = ans - vec.at(N-1);
       vec.at(N - 1) = 0;
     }
      if( (S.at(N - 1) == ti) & (di == 'L')){
       vec.at(N - 2) = ( vec.at(N - 1) + vec.at(N-2) );
     ​  vec.at(N - 1) =0; 
     }
      for (int j=1; j<(N-1); j++){
        if( (S.at(j) == ti) & (di == 'R')){
          vec.at(j+1) = ( vec.at(j+1) + vec.at(j) );
          vec.at(j)=0;
        }
         if( (S.at(j) == ti) & (di == 'L')){
          vec.at(j-1) = ( vec.at(j-1) + vec.at(j) );
          vec.at(j)=0;
        }
      }
 }
  cout << ans << endl;
        
}
