#include <bits/stdc++.h>
using namespace std;
void __print(int x) { cout << x; }
void __print(long x) { cout << x; }
void __print(long long x) { cout << x; }
void __print(unsigned x) { cout << x; }
void __print(unsigned long x) { cout << x; }
void __print(unsigned long long x) { cout << x; }
void __print(float x) { cout << x; }
void __print(double x) { cout << x; }
void __print(long double x) { cout << x; }
void __print(char x) { cout << '\'' << x << '\''; }
void __print(const char *x) { cout << '\"' << x << '\"'; }
void __print(const string &x) { cout << '\"' << x << '\"'; }
void __print(bool x) { cout << (x ? "true" : "false"); }
template <typename T, typename V>
void __print(const pair<T, V> &x) {
  __print(x.first);
  cout << ',';
  __print(x.second);
}
template <typename T>
void __print(const T &x) {
  int f = 0;
  for (auto &i : x) cout << (f++ ? "," : ""), __print(i);
}
void _print() { cout << "]\n"; }
template <typename T, typename... V>
void _print(T t, V... v) {
  __print(t);
  if (sizeof...(v)) cout << ", ";
  _print(v...);
}
const int N = 2e5 + 7;
const int MOD = 1e9 + 7;
long long fastpow(long long b, long long p) {
  long long temp;
  if (p == 0) return 1;
  if (p == 1) return b;
  temp = fastpow(b, p / 2);
  temp = temp * temp % MOD;
  if (p & 1) {
    temp = temp * b % MOD;
  }
  return temp;
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  long long n, k;
  cin >> n >> k;
  string s;
  cin >> s;
  vector<char> v(k);
  for (int i = 0; i < k; i++) cin >> v[i];
  vector<int> temp(n);
  for (int i = 0; i < n; i++) {
    if (count(v.begin(), v.end(), s[i]))
      temp[i] = 1;
    else
      temp[i] = 0;
  }
  long long ans = 0;
  for (int i = 0; i < n; i++) {
    if (temp[i] == 1) {
      long long j = i;
      while (j < n && temp[j] == 1) j++;
      ans += ((j - i) * (j - i + 1)) / 2;
      i = j;
    }
  }
  cout << ans;
  return 0;
}
