#include <bits/stdc++.h>
using namespace std;
ifstream fin("rumbal.in");
ofstream fout("rumbal.out");
int n, m, k;
char ch, depl;
char s[200005];
int x[200005];
int main()
{
    fin >> n >> m;
    for (int i = 1; i <= n; i++)
    {
        fin >> ch;
        s[i] = ch;
        x[i] = 1;
    }
    for (int i = 1; i <= m; i++)
    {
        fin >> ch >> depl;
        if (depl == 'D')
        {
            for (int j = 1; j <= n; j++)
            {
                if (s[j] == ch)
                {
                    if (j == n)
                    {
                        k += x[j];
                        x[j] = 0;
                    }
                    else if(x[j])
                    {
                        x[j+1] += x[j];
                        x[j] = 0;
                    }
                }
            }
        }
        else
        {
            for (int j = 1; j <= n; j++)
            {
                if (s[j] == ch)
                {
                    if (j == 1)
                    {
                        k += x[j];
                        x[j] = 0;
                    }
                    else if (x[j])
                    {
                        x[j-1] += x[j];
                        x[j] = 0;
                    }
                }
            }
        }
    }
    fout << n - k;
}