import java.util.*;
public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
	    int [] in = new int [4];
	    for(int i=0;i<4;i++){in[i] = sc.nextInt();}
        Arrays.sort(in);
		if(in[3]-in[2]==1 && in[2]-in[1]==1 && in[1]-in[0]==1){System.out.println("Yes");}
        else{System.out.println("No");}
	}
}