#include<cstdio>
#include<algorithm>
#include<cstring>
using namespace std;
int gi(){
	int x=0,w=1;char ch=getchar();
	while((ch<'0'||ch>'9')&&ch!='-')ch=getchar();
	if(ch=='-')w=0,ch=getchar();
	while(ch>='0'&&ch<='9')x=(x<<3)+(x<<1)+ch-'0',ch=getchar();
	return w?x:-x;
}
char gc(){
	char ch=getchar();
	while(ch<'A'||ch>'Z')ch=getchar();
	return ch;
}
const int N=2e5+5;
int n,m;char s[N],a[N],b[N];

int check(int x){
	for(int i=1;i<=m;++i)
		if(s[x]==a[i]){
			x+=b[i]=='L'?-1:1;
			if(x<1)return 1;
			if(x>n)return -1;
		}
	return 0;
}
int main(){
	n=gi();m=gi();scanf("%s",s+1);
	for(int i=1;i<=m;++i)a[i]=gc(),b[i]=gc();
	int l,r,L=0,R=n+1;
	l=1;r=n;while(l<=r){
		int mid=l+r>>1;
		if(check(mid)==1)L=mid,l=mid+1;
		else r=mid-1;
	}
	l=1,r=n;while(l<=r){
		int mid=l+r>>1;
		if(check(mid)==-1)R=mid,r=mid-1;
		else l=mid+1;
	}
	printf("%d\n",n-min(n,L+n+1-R));
	return 0;
}
