import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int N = scan.nextInt();
		String S = scan.next();
		scan.close();
		if(N == 1) {
			System.out.println("NO");
		}else if(N == 2) {
			if(S.equals("01") || S.equals("10")) {
				System.out.println("NO");
			}else {
				System.out.println("YES");
			}
		}else if(N == 3) {
			if(S.equals("010") || S.equals("101")) {
				System.out.println("NO");
			}else {
				System.out.println("YES");
			}
		}else {
			System.out.println("YES");
		}
	}
}