import java.util.*;
import java.util.Scanner;

class Main {

    public static void main(String args[]) {
        Scanner sc = new Scanner(System.in);
        final int N = sc.nextInt();
        int[] H = new int[N];

        for(int i=0;i<N;i++){
            H[i]=sc.nextInt()-1;
        }

        for(int i=0;i<N-1;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.*; util.* java import java.util.Scanner; Scanner java.util class Main {

    public static void main(String args[]) {
        Scanner sc = new Scanner(System.in);
        final int N = sc.nextInt();
        int[] H = new int[N];

        for(int i=0;i<N;i++){
            H[i]=sc.nextInt()-1;
        }

        for(int i=0;i<N-1;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);
        final int N = sc.nextInt();
        int[] H = new int[N];

        for(int i=0;i<N;i++){
            H[i]=sc.nextInt()-1;
        }

        for(int i=0;i<N-1;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);
        final int N = sc.nextInt();
        int[] H = new int[N];

        for(int i=0;i<N;i++){
            H[i]=sc.nextInt()-1;
        }

        for(int i=0;i<N-1;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) final int N = sc.nextInt(); N sc.nextInt() sc.nextInt sc int[] H = new int[N]; H new int[N] N for(int i=0;i<N;i++){
            H[i]=sc.nextInt()-1;
        } int i=0; int i=0; i 0 i<N i N i++ i++ i {
            H[i]=sc.nextInt()-1;
        } {
            H[i]=sc.nextInt()-1;
        } H[i]=sc.nextInt()-1 H[i] H i sc.nextInt()-1 sc.nextInt() sc.nextInt sc 1 for(int i=0;i<N-1;i++){
            if(H[i]>H[i+1]){
                H[i+1]++;
                if(H[i]>H[i+1]){
                    System.out.println("No");
                    return;
                }
            }
        } 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]){
                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]++;
                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 {
                H[i+1]++;
                if(H[i]>H[i+1]){
                    System.out.println("No");
                    return;
                }
            } 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
import java.util.*;
import java.util.Scanner;

class Main {

    public static void main(String args[]) {
        Scanner sc = new Scanner(System.in);
        final int N = sc.nextInt();
        int[] H = new int[N];

        for(int i=0;i<N;i++){
            H[i]=sc.nextInt()-1;
        }

        for(int i=0;i<N-1;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");
    }
}