#include <iostream>
#include <string>
#define int long long
using namespace std;
int k; string s; char l, r;
int cnt, ans;
signed main() {
cin >> k >> s >> l >> r;
for(int i = k-1; i < (int)s.length(); i++) {
cnt += s[i-k+1] == l;
ans += cnt * (s[i] == r);
}
cout << ans << endl;
return 0;
}