#include <bits/stdc++.h>
using namespace std;
const int INF = 100005;
const long long LL_INF = (long long)2e18 + 5;
inline int gcd(int a, int b) { return b == 0 ? a : gcd(b, a % b); }
const long long mod = 1000000007;
bool isprime(long long n) {
  for (long long i = 2; i * i <= n; ++i) {
    if (n % i == 0) {
      return false;
    }
  }
  return true;
}
long long factorial(long long n) {
  return (n == 1 || n == 0) ? 1 : n * factorial(n - 1);
}
long long power(long long x, long long y) {
  long long res = 1;
  x = x % mod;
  while (y > 0) {
    if (y & 1) res = ((res % mod) * (x % mod)) % mod;
    y = y >> 1;
    x = ((x % mod) * (x % mod)) % mod;
  }
  return res;
}
long long ncr(long long n, long long r) {
  long long res = 1;
  if (r > n) return 0;
  if (r > n - r) r = n - r;
  for (long long i = 0; i < r; i++) {
    res = ((res % mod) * ((n - i) % mod)) % mod;
    res = ((res % mod) * (power(i + 1, mod - 2)) % mod) % mod;
  }
  return res;
}
long long gcd(long long a, long long b) {
  if (a == 0) return b;
  return gcd(b % a, a);
}
long long lcm(long long a, long long b) { return (a / gcd(a, b) * b); }
long long max(long long a, long long b) {
  long long sol = a > b ? a : b;
  return sol;
}
long long min(long long a, long long b) {
  long long sol = a < b ? a : b;
  return sol;
}
map<long long, long long> mp;
inline void solve() {
  long long n, k;
  long long a[26] = {0};
  cin >> n >> k;
  string s;
  cin >> s;
  char ch;
  while (k--) {
    cin >> ch;
    a[ch - 'a']++;
  }
  long long prev = -1, r;
  long long ans = 0;
  for (int i = 0; i < n; i++) {
    if (a[s[i] - 'a'] == 0) {
      r = i - prev - 1;
      ans += ((r * (r + 1)) / 2);
      prev = i;
    }
  }
  r = n - prev - 1;
  ans += ((r * (r + 1)) / 2);
  cout << ans;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  ;
  solve();
}
