import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in) ;
        int n = in.nextInt();
        boolean flag = true;
        String s = in.next();
        for (int i = 0; i < n - 1; i++){
            if (s.charAt(i) > s.charAt(i + 1)){
                System.out.println("YES");
                System.out.println((i + 1) + " " + (i + 2));
                return;
            }
        }
        System.out.println("NO");
    }
}
