#include <bits/stdc++.h>
using namespace std;
#define int long long
constexpr int N = 57, M = 11;
constexpr int inf = 1E18, mod = 1e9 + 7;
inline void Main() {
    int n; cin >> n;
    string s; char st, ed;
    cin >> s >> st >> ed;
    vector<int> pre, suf;
    int len = s.size();
    for (int i = 0; i < len; i ++) {
        if(s[i] == st) pre.push_back(i);
        if(s[i] == ed) suf.push_back(i);
    }
    len = pre.size();
    int ans = 0;
    for (int i = 0; i < len; i ++) {
        int x = pre[i];
        int d = x + n - 1;
        int l = 0, r = suf.size() - 1;
        while(l < r) {
            int mid = l + r >> 1;
            if(suf[mid] >= d) r = mid;
            else l = mid + 1;
        }
        if(suf[r] >= d) ans += (suf.size() - r);
    }
    cout << ans << '\n';
}
signed main() {    
    cin.tie(nullptr)->sync_with_stdio(false);
    int T = 1;
    while(T --) Main();
    return 0;
}