import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N = Integer.parseInt(sc.next());
        int pre = 0;
        String r = "Yes";
        for (int i = 0; i < N; i++) {
            int h = Integer.parseInt(sc.next());
            if (pre > h) {
                h++;
                if (pre > h) r = "No";
            }
            pre = h;
        }
        System.out.println(r);
    }
}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz