/**
 *    author:   raghuvanshraj
 *    created:  18.02.2020 06:54:07 PM
**/
#include <bits/stdc++.h>

#define MOD 1000000007

#define init_arr(arr,n,val) for (int i = 0; i < n; ++i) arr[i] = val
#define init_arr2d(arr,n,m,val) for (int i = 0; i < n; ++i) for (int j = 0; j < m; ++j) arr[i][j] = val
#define init_arr3d(arr,n,m,l,val) for (int i = 0; i < n; ++i) for (int j = 0; j < n; ++j) for (int k = 0; k < l; ++k) arr[i][j][k] = val
#define input_arr(arr,n) for (int i = 0; i < n; ++i) cin >> arr[i];
#define input_arr2d(arr,n,m) for (int i = 0; i < n; ++i) for (int j = 0; j < m; ++j) cin >> arr[i][j];
#define input_arr3d(arr,n,m,l,val) for (int i = 0; i < n; ++i) for (int j = 0; j < n; ++j) for (int k = 0; k < l; ++k) cin >> arr[i][j][k];
#define print_arr(arr,n) for (int i = 0; i < n; ++i) cout << arr[i] << ' '; cout << endl
#define print_arr2d(arr,n,m) for (int i = 0; i < n; ++i) { for (int j = 0; j < m; ++j) cout << arr[i][j] << ' '; cout << endl; }

#define all(v) v.begin(), v.end()
#define dec(a,t,n) t *a = new t[n]()
#define dec2d(a,t,n,m) t **a = new t*[n](); for (int i = 0; i < n; ++i) a[i] = new t[m]()
#define pb push_back
#define mp make_pair
#define ff first
#define ss second

using namespace std;

typedef long long ll;
typedef unsigned long ul;
typedef unsigned long long ull;
typedef long double ld;
typedef vector<int> vi;
typedef vector<string> vs;
typedef queue<int> qi;
typedef priority_queue<int> max_heap;
typedef priority_queue<int, vector<int>, greater<int>> min_heap;
typedef pair<int,int> pii;
typedef pair<string,int> psi;
typedef map<string,int> msi;
typedef map<int,int> mii;
typedef unordered_map<string,int> umsi;
typedef unordered_map<int,int> umii;
typedef set<int> si;
typedef unordered_set<int> usi;

template <
    typename T,
    typename = typename enable_if<is_arithmetic<T>::value, T>::type,
    typename U,
    typename = typename enable_if<is_arithmetic<T>::value, T>::type
>
pair<T,U> operator+(const pair<T,U> &a, const pair<T,U> &b) {
    return {a.first + b.first, a.second + b.second};
}

template <
    typename T,
    typename = typename enable_if<is_arithmetic<T>::value, T>::type,
    typename U,
    typename = typename enable_if<is_arithmetic<T>::value, T>::type
>
pair<T,U> operator-(const pair<T,U> &a, const pair<T,U> &b) {
    return {a.first - b.first, a.second - b.second};
}

int main(int argc, char const *argv[]) {
    ios::sync_with_stdio(false);
    cin.tie(0);

    int n,k;
    cin >> n >> k;
    string s;
    cin >> s;
    set<char> available;
    while (k--) {
        char ch;
        cin >> ch;
        available.insert(ch);
    }

    vector<int> end_here(n);
    init_arr(end_here, n, i+1);
    int curr_minus = 0;
    for (int i = 0; i < n; ++i) {
        end_here[i] -= curr_minus;
        if (available.find(s[i]) == available.end()) {
            end_here[i] = 0;
            curr_minus = i+1;
        }
    }

    long ans = 0;
    for (int i = 0; i < n; ++i) {
        ans += (long)end_here[i];
    }

    cout << ans;

    return 0;
}