import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.stream.Stream;

public class Main {

    public static void main(String[] args) throws Exception {

        InputStreamReader is = new InputStreamReader(System.in);
        BufferedReader reader = new BufferedReader(is);

        List<String> mylist = new ArrayList<>();

        // 標準入力からの値を変数strinputに代入
        String strinput = reader.readLine();

        while (strinput != null) {

            mylist.add(strinput);
            strinput = reader.readLine();

        }

        String arr[] = mylist.get(0).split(" ");
        Stream<String> stream = Arrays.stream(arr);
        int arr02[] = stream.mapToInt(Integer::parseInt).toArray();
        int l = arr.length;
        Arrays.sort(arr02);
        Boolean chkflg = true;
        for (int i = 0; i < l - 1; i++) {
            int a = Integer.valueOf(arr02[i]);
            int b = Integer.valueOf(arr02[i + 1]);

            if (b - a != 1) {
                chkflg = false;
                break;
            }

        }
        System.out.println(chkflg ? "Yes" : "No");
    }

}