import java.io.PrintWriter;

import java.util.*;

public class Main {

    public static final int MAXN=100000+5;

    public static int v[]=new int [MAXN];

    public static void main(String[] args) {

        Scanner cin = new Scanner(System.in);

        PrintWriter out = new PrintWriter(System.out);

        int n=cin.nextInt(),m=cin.nextInt();

        out.println(Math.max(n,m)-Math.min(n,m)<=1&&(n>0||m>0)?"YES":"NO");

        cin.close();

        out.flush();

    }

}