
import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] a = new int[n];
        for(int i=0;i<n;i++){
            a[n-i-1] = sc.nextInt();
        }
        for(int i=0;i<n-1;i++){
            int tmp = a[i+1] - a[i];
            if(tmp > 1){
                System.out.println("No");
                return;
            }
            if(tmp > 0){
                a[i+1]--;
            }
        }
        System.out.println("Yes");
    }
} import java.util.*; util.* java public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] a = new int[n];
        for(int i=0;i<n;i++){
            a[n-i-1] = sc.nextInt();
        }
        for(int i=0;i<n-1;i++){
            int tmp = a[i+1] - a[i];
            if(tmp > 1){
                System.out.println("No");
                return;
            }
            if(tmp > 0){
                a[i+1]--;
            }
        }
        System.out.println("Yes");
    }
} Main public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] a = new int[n];
        for(int i=0;i<n;i++){
            a[n-i-1] = sc.nextInt();
        }
        for(int i=0;i<n-1;i++){
            int tmp = a[i+1] - a[i];
            if(tmp > 1){
                System.out.println("No");
                return;
            }
            if(tmp > 0){
                a[i+1]--;
            }
        }
        System.out.println("Yes");
    } main {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] a = new int[n];
        for(int i=0;i<n;i++){
            a[n-i-1] = sc.nextInt();
        }
        for(int i=0;i<n-1;i++){
            int tmp = a[i+1] - a[i];
            if(tmp > 1){
                System.out.println("No");
                return;
            }
            if(tmp > 0){
                a[i+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[] a = new int[n]; a new int[n] n for(int i=0;i<n;i++){
            a[n-i-1] = sc.nextInt();
        } int i=0; int i=0; i 0 i<n i n i++ i++ i {
            a[n-i-1] = sc.nextInt();
        } {
            a[n-i-1] = sc.nextInt();
        } a[n-i-1] = sc.nextInt() a[n-i-1] a n-i-1 n-i-1 n i 1 sc.nextInt() sc.nextInt sc for(int i=0;i<n-1;i++){
            int tmp = a[i+1] - a[i];
            if(tmp > 1){
                System.out.println("No");
                return;
            }
            if(tmp > 0){
                a[i+1]--;
            }
        } int i=0; int i=0; i 0 i<n-1 i n-1 n 1 i++ i++ i {
            int tmp = a[i+1] - a[i];
            if(tmp > 1){
                System.out.println("No");
                return;
            }
            if(tmp > 0){
                a[i+1]--;
            }
        } {
            int tmp = a[i+1] - a[i];
            if(tmp > 1){
                System.out.println("No");
                return;
            }
            if(tmp > 0){
                a[i+1]--;
            }
        } int tmp = a[i+1] - a[i]; tmp a[i+1] - a[i] a[i+1] a i+1 i 1 a[i] a i if(tmp > 1){
                System.out.println("No");
                return;
            } tmp > 1 tmp 1 {
                System.out.println("No");
                return;
            } System.out.println("No") System.out.println System.out System System.out "No" return; if(tmp > 0){
                a[i+1]--;
            } tmp > 0 tmp 0 {
                a[i+1]--;
            } a[i+1]-- a[i+1] a i+1 i 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) throws Exception {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] a = new int[n];
        for(int i=0;i<n;i++){
            a[n-i-1] = sc.nextInt();
        }
        for(int i=0;i<n-1;i++){
            int tmp = a[i+1] - a[i];
            if(tmp > 1){
                System.out.println("No");
                return;
            }
            if(tmp > 0){
                a[i+1]--;
            }
        }
        System.out.println("Yes");
    }
} public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] a = new int[n];
        for(int i=0;i<n;i++){
            a[n-i-1] = sc.nextInt();
        }
        for(int i=0;i<n-1;i++){
            int tmp = a[i+1] - a[i];
            if(tmp > 1){
                System.out.println("No");
                return;
            }
            if(tmp > 0){
                a[i+1]--;
            }
        }
        System.out.println("Yes");
    }
} Main

import java.util.*;

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