
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        final Scanner scanner = new Scanner(System.in);
        final int counter = scanner.nextInt();

        int left = 0;
        for (int i = 0; i < counter; i++) {
            final int stair = scanner.nextInt() - 1;
            if (stair >= left) {
                left = stair;
            } else {
                if (left > stair + 1) {
                    System.out.println("No");
                    return;
                }
            }
        }

        System.out.println("Yes");
    }
}

/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