import java.util.Scanner;
import java.util.regex.Pattern;

public class DigitString {

    /*
     * Problem -A String is given. You need to check if it contains only digits.
     * Approach - regular expressions
     */


    public static boolean containsDigits(String str) {
        String regex = "\\d*";
        return Pattern.matches(regex, str);
    }


    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);
        System.out.print("Enter a string : ");
        String str = sc.nextLine();

        if (containsDigits(str))
            System.out.println("YES");
        else
            System.out.println("NO");

        sc.close();
    }
}
