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[] h = new int[n];
        for (int i = 0; i < n; i++) {
            h[i] = Integer.parseInt(sc.next());
        }
        for (int i = n - 1; i > 0; i--) {
            if (h[i] < h[i - 1]) {
                h[i - 1]--;
            }
            if (h[i] < h[i - 1]) {
                System.out.println("No");
                return;
            }
        }
        System.out.println("Yes");
    }
} import java.util.Scanner; Scanner java.util public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = Integer.parseInt(sc.next());
        int[] h = new int[n];
        for (int i = 0; i < n; i++) {
            h[i] = Integer.parseInt(sc.next());
        }
        for (int i = n - 1; i > 0; i--) {
            if (h[i] < h[i - 1]) {
                h[i - 1]--;
            }
            if (h[i] < h[i - 1]) {
                System.out.println("No");
                return;
            }
        }
        System.out.println("Yes");
    }
} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = Integer.parseInt(sc.next());
        int[] h = new int[n];
        for (int i = 0; i < n; i++) {
            h[i] = Integer.parseInt(sc.next());
        }
        for (int i = n - 1; i > 0; i--) {
            if (h[i] < h[i - 1]) {
                h[i - 1]--;
            }
            if (h[i] < h[i - 1]) {
                System.out.println("No");
                return;
            }
        }
        System.out.println("Yes");
    } main {
        Scanner sc = new Scanner(System.in);
        int n = Integer.parseInt(sc.next());
        int[] h = new int[n];
        for (int i = 0; i < n; i++) {
            h[i] = Integer.parseInt(sc.next());
        }
        for (int i = n - 1; i > 0; i--) {
            if (h[i] < h[i - 1]) {
                h[i - 1]--;
            }
            if (h[i] < h[i - 1]) {
                System.out.println("No");
                return;
            }
        }
        System.out.println("Yes");
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n = Integer.parseInt(sc.next()); n Integer.parseInt(sc.next()) Integer.parseInt Integer sc.next() sc.next sc int[] h = new int[n]; h new int[n] n for (int i = 0; i < n; i++) {
            h[i] = Integer.parseInt(sc.next());
        } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
            h[i] = Integer.parseInt(sc.next());
        } {
            h[i] = Integer.parseInt(sc.next());
        } h[i] = Integer.parseInt(sc.next()) h[i] h i Integer.parseInt(sc.next()) Integer.parseInt Integer sc.next() sc.next sc for (int i = n - 1; i > 0; i--) {
            if (h[i] < h[i - 1]) {
                h[i - 1]--;
            }
            if (h[i] < h[i - 1]) {
                System.out.println("No");
                return;
            }
        } int i = n - 1; int i = n - 1; i n - 1 n 1 i > 0 i 0 i-- i-- i {
            if (h[i] < h[i - 1]) {
                h[i - 1]--;
            }
            if (h[i] < h[i - 1]) {
                System.out.println("No");
                return;
            }
        } {
            if (h[i] < h[i - 1]) {
                h[i - 1]--;
            }
            if (h[i] < h[i - 1]) {
                System.out.println("No");
                return;
            }
        } if (h[i] < h[i - 1]) {
                h[i - 1]--;
            } h[i] < h[i - 1] h[i] h i h[i - 1] h i - 1 i 1 {
                h[i - 1]--;
            } h[i - 1]-- h[i - 1] h i - 1 i 1 if (h[i] < h[i - 1]) {
                System.out.println("No");
                return;
            } h[i] < h[i - 1] h[i] h i h[i - 1] h i - 1 i 1 {
                System.out.println("No");
                return;
            } System.out.println("No") System.out.println System.out System System.out "No" return; System.out.println("Yes") System.out.println System.out System System.out "Yes" String[] args args public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = Integer.parseInt(sc.next());
        int[] h = new int[n];
        for (int i = 0; i < n; i++) {
            h[i] = Integer.parseInt(sc.next());
        }
        for (int i = n - 1; i > 0; i--) {
            if (h[i] < h[i - 1]) {
                h[i - 1]--;
            }
            if (h[i] < h[i - 1]) {
                System.out.println("No");
                return;
            }
        }
        System.out.println("Yes");
    }
} public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = Integer.parseInt(sc.next());
        int[] h = new int[n];
        for (int i = 0; i < n; i++) {
            h[i] = Integer.parseInt(sc.next());
        }
        for (int i = n - 1; i > 0; i--) {
            if (h[i] < h[i - 1]) {
                h[i - 1]--;
            }
            if (h[i] < h[i - 1]) {
                System.out.println("No");
                return;
            }
        }
        System.out.println("Yes");
    }
} Main
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[] h = new int[n];
        for (int i = 0; i < n; i++) {
            h[i] = Integer.parseInt(sc.next());
        }
        for (int i = n - 1; i > 0; i--) {
            if (h[i] < h[i - 1]) {
                h[i - 1]--;
            }
            if (h[i] < h[i - 1]) {
                System.out.println("No");
                return;
            }
        }
        System.out.println("Yes");
    }
}