#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef double lf;
typedef pair<ll,ll> ii;
#define REP(i,n) for(int i=0;i<n;i++)
#define REP1(i,n) for(ll i=1;i<=n;i++)
#define RST(i,n) memset(i,n,sizeof i)
#define SZ(a) (int)a.size()
#define ALL(a) a.begin(),a.end()
#define X first
#define Y second
#define mkp make_pair
#define pb push_back
#define eb emplace_back
#define pob pop_back
#ifdef cold66
#define debug(...) do{\
    fprintf(stderr,"%s - %d (%s) = ",__PRETTY_FUNCTION__,__LINE__,#__VA_ARGS__);\
    _do(__VA_ARGS__);\
}while(0)
template<typename T>void _do(T &&_x){cerr<<_x<<endl;}
template<typename T,typename ...S> void _do(T &&_x,S &&..._t){cerr<<_x<<", ";_do(_t...);}
template<typename _a,typename _b> ostream& operator << (ostream &_s,const pair<_a,_b> &_p){return _s<<"("<<_p.X<<","<<_p.Y<<")";}
template<typename It> ostream& _OUTC(ostream &_s,It _ita,It _itb)
{
    _s<<"{";
    for(It _it=_ita;_it!=_itb;_it++)
    {
        _s<<(_it==_ita?"":",")<<*_it;
    }
    _s<<"}";
    return _s;
}
template<typename _a> ostream &operator << (ostream &_s,vector<_a> &_c){return _OUTC(_s,ALL(_c));}
template<typename _a> ostream &operator << (ostream &_s,set<_a> &_c){return _OUTC(_s,ALL(_c));}
template<typename _a,typename _b> ostream &operator << (ostream &_s,map<_a,_b> &_c){return _OUTC(_s,ALL(_c));}
template<typename _t> void pary(_t _a,_t _b){_OUTC(cerr,_a,_b);cerr<<endl;}
#define IOS()
#else
#define debug(...)
#define pary(...)
#define endl '\n'
#define IOS() ios_base::sync_with_stdio(0);cin.tie(0);
#endif // cold66
//}
template<class T> inline bool chkmax(T &a, const T &b) { return b > a ? a = b, true : false; }
template<class T> inline bool chkmin(T &a, const T &b) { return b < a ? a = b, true : false; }
template<class T> using MaxHeap = priority_queue<T>;
template<class T> using MinHeap = priority_queue<T, vector<T>, greater<T>>;

const ll MAXn=1e5+5,MAXlg=__lg(MAXn)+2;
const ll MOD=1000000007;
const ll INF=0x3f3f3f3f;

string s,a,b;
bool chk1(ll x){
    string tmp = s.substr(0,x);
    debug(tmp);
    ll idx = 0, cnt = 0;
    for (ll i=SZ(tmp)-1;i>=0;i--) {
        while (idx < SZ(a) && tmp[i] != a[idx]) idx++;
        if (idx >= SZ(a)) break;
        if (tmp[i] == a[idx]) cnt++,idx++;
    }
    debug(cnt);
    return (cnt == SZ(tmp));
}
bool chk2(ll x){
    string tmp = s.substr(SZ(s)-x,x);
    debug(tmp);
    ll idx = 0, cnt = 0;
    REP (i,SZ(tmp)) {
        while (idx < SZ(b) && tmp[i] != b[idx]) idx++;
        if (idx >= SZ(b)) break;
        if (tmp[i] == b[idx]) cnt++,idx++;
    }
    debug(cnt);
    return (cnt == SZ(tmp));
}
int main(){
    IOS();
    ll n,q;
    cin >> n >> q;
    cin >> s;
    REP (i,q) {
        char t,d;
        cin >> t >> d;
        if (d == 'L') a += t;
        else b += t;
    }
    debug(a,b);

    ll l=0,r=n+1;
    while (l != r-1) {
        ll mid = (l+r)>>1;
        if (chk1(mid)) l = mid;
        else r = mid;
    }
    debug(l,r);
    ll l1=0,r1=n+1;
    while (l1 != r1-1) {
        debug(l1,r1);
        ll mid = (l1+r1)>>1;
        if (chk2(mid)) l1 = mid;
        else r1 = mid;
    }
    debug(l1,r1);
    cout << max(0LL,n-l-l1) << endl;
}
