import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        final Scanner scanner = new Scanner(System.in);
        final double minimum = scanner.nextDouble();
        scanner.nextLine();
        final String a = scanner.nextLine(), b = scanner.nextLine();
        final int length = a.length();
        int same = 0;
        for (int i = 0; i < length; i++) {
            if (a.charAt(i) != b.charAt(i)) continue;
            same++;
        }
        double rate = (double) same / length;
        System.out.println(rate >= minimum ? "yes" : "no");
    }
}