import java.util.Scanner;

public class Main {

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

        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 = sc.nextInt();
        int[] h = new int[n];
        int[] d = new int[n];
        for (int i = 0 ; i < n ; i++) {
            h[i] = sc.nextInt();
        }
        if (n == 1) {
            System.out.println("Yes");
            return;
        }
        h[0] -= 1;
        for (int i = 0 ; i < n - 1 ; i++) {
            if (h[i] - h[i + 1] >= 1) {
                System.out.println("No");
                return;
            }
            if (h[i] < h[i + 1]) {
                h[i + 1] -= 1;
            }
        }

        System.out.println("Yes");

    }

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

        System.out.println("Yes");

    } main {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] h = new int[n];
        int[] d = new int[n];
        for (int i = 0 ; i < n ; i++) {
            h[i] = sc.nextInt();
        }
        if (n == 1) {
            System.out.println("Yes");
            return;
        }
        h[0] -= 1;
        for (int i = 0 ; i < n - 1 ; i++) {
            if (h[i] - h[i + 1] >= 1) {
                System.out.println("No");
                return;
            }
            if (h[i] < h[i + 1]) {
                h[i + 1] -= 1;
            }
        }

        System.out.println("Yes");

    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc int[] h = new int[n]; h new int[n] n int[] d = new int[n]; d new int[n] n for (int i = 0 ; i < n ; i++) {
            h[i] = sc.nextInt();
        } int i = 0 ; int i = 0 ; i 0 i < n i n i++ i++ i {
            h[i] = sc.nextInt();
        } {
            h[i] = sc.nextInt();
        } h[i] = sc.nextInt() h[i] h i sc.nextInt() sc.nextInt sc if (n == 1) {
            System.out.println("Yes");
            return;
        } n == 1 n 1 {
            System.out.println("Yes");
            return;
        } System.out.println("Yes") System.out.println System.out System System.out "Yes" return; h[0] -= 1 h[0] h 0 1 for (int i = 0 ; i < n - 1 ; i++) {
            if (h[i] - h[i + 1] >= 1) {
                System.out.println("No");
                return;
            }
            if (h[i] < h[i + 1]) {
                h[i + 1] -= 1;
            }
        } int i = 0 ; int i = 0 ; i 0 i < n - 1 i n - 1 n 1 i++ i++ i {
            if (h[i] - h[i + 1] >= 1) {
                System.out.println("No");
                return;
            }
            if (h[i] < h[i + 1]) {
                h[i + 1] -= 1;
            }
        } {
            if (h[i] - h[i + 1] >= 1) {
                System.out.println("No");
                return;
            }
            if (h[i] < h[i + 1]) {
                h[i + 1] -= 1;
            }
        } if (h[i] - h[i + 1] >= 1) {
                System.out.println("No");
                return;
            } h[i] - h[i + 1] >= 1 h[i] - h[i + 1] h[i] h i h[i + 1] h i + 1 i 1 1 {
                System.out.println("No");
                return;
            } System.out.println("No") System.out.println System.out System System.out "No" return; if (h[i] < h[i + 1]) {
                h[i + 1] -= 1;
            } h[i] < h[i + 1] h[i] h i h[i + 1] h i + 1 i 1 {
                h[i + 1] -= 1;
            } h[i + 1] -= 1 h[i + 1] h i + 1 i 1 1 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 = sc.nextInt();
        int[] h = new int[n];
        int[] d = new int[n];
        for (int i = 0 ; i < n ; i++) {
            h[i] = sc.nextInt();
        }
        if (n == 1) {
            System.out.println("Yes");
            return;
        }
        h[0] -= 1;
        for (int i = 0 ; i < n - 1 ; i++) {
            if (h[i] - h[i + 1] >= 1) {
                System.out.println("No");
                return;
            }
            if (h[i] < h[i + 1]) {
                h[i + 1] -= 1;
            }
        }

        System.out.println("Yes");

    }

} public class Main {

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

        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 = sc.nextInt();
        int[] h = new int[n];
        int[] d = new int[n];
        for (int i = 0 ; i < n ; i++) {
            h[i] = sc.nextInt();
        }
        if (n == 1) {
            System.out.println("Yes");
            return;
        }
        h[0] -= 1;
        for (int i = 0 ; i < n - 1 ; i++) {
            if (h[i] - h[i + 1] >= 1) {
                System.out.println("No");
                return;
            }
            if (h[i] < h[i + 1]) {
                h[i + 1] -= 1;
            }
        }

        System.out.println("Yes");

    }

}