import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;

public class Main {

public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int k = sc.nextInt();
    String str = sc.next();
    char c1 = sc.next().charAt(0);
    char c2 = sc.next().charAt(0);
    char[] c = str.toCharArray();


    //快慢指针
    int l=0,r=k-1;
    long cnt=0;
    long ans=0;

    while(true) {
        if(r==c.length) {
            break;
        }

        if(c[l]==c1) {
            cnt++;
        }
        if(c[r]==c2) {
            ans+=cnt;
        }

        l++;
        r++;
    }
    System.out.println(ans);
}

}