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

int main()
{
  long long q,n;
  cin >>q>>n;
  string s;
  cin>>s;
  long long c[26];
  vector<long long> v;
  vector<long long> z;
  for (long long i=0;i<26;i++)
  {
    c[i]=0;
  }
  for (long long i=0;i<n;i++)
  {
    char p;
    cin>>p;
    c[p-'a']=1;
  }
  for (long long i=0; i<s.size();i++)
  {
    v.push_back(c[s[i]-'a']);

  }
  v.push_back(0);

  long long sum =0;

  for (long long i=0;i<v.size()-1;i++)
  {

    if (v[i]==0)z.push_back(0);
    else if (v[i]==1 && v[i+1]==1)sum+=1;
    else if (v[i]==1 && v[i+1]==0 )z.push_back(sum+1),sum=0;
  }
  z.push_back(sum);
  /*for (long long i=0;i<z.size();i++)
  {
    cout<<z[i];
  }*/
  long long jawaban=0;
  for (long long i=0;i<z.size();i++)
  {
    jawaban += (z[i]*(z[i]+1))/2;
  }
  cout<< jawaban;
}