import java.util.*;
class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] h = new int[n];
        for(int i = 0; i<n; i++) {
            h[i] = sc.nextInt();
        }
        int max = h[0];
        for(int i = 1; i<n; i++) {
            if(max-h[i]>=2) {
                System.out.println("No");
                return;
            }
            max = Math.max(max, h[i]);
        }
        System.out.println("Yes");

    }
} import java.util.*; util.* java class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] h = new int[n];
        for(int i = 0; i<n; i++) {
            h[i] = sc.nextInt();
        }
        int max = h[0];
        for(int i = 1; i<n; i++) {
            if(max-h[i]>=2) {
                System.out.println("No");
                return;
            }
            max = Math.max(max, h[i]);
        }
        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];
        for(int i = 0; i<n; i++) {
            h[i] = sc.nextInt();
        }
        int max = h[0];
        for(int i = 1; i<n; i++) {
            if(max-h[i]>=2) {
                System.out.println("No");
                return;
            }
            max = Math.max(max, h[i]);
        }
        System.out.println("Yes");

    } main {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] h = new int[n];
        for(int i = 0; i<n; i++) {
            h[i] = sc.nextInt();
        }
        int max = h[0];
        for(int i = 1; i<n; i++) {
            if(max-h[i]>=2) {
                System.out.println("No");
                return;
            }
            max = Math.max(max, h[i]);
        }
        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 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 int max = h[0]; max h[0] h 0 for(int i = 1; i<n; i++) {
            if(max-h[i]>=2) {
                System.out.println("No");
                return;
            }
            max = Math.max(max, h[i]);
        } int i = 1; int i = 1; i 1 i<n i n i++ i++ i {
            if(max-h[i]>=2) {
                System.out.println("No");
                return;
            }
            max = Math.max(max, h[i]);
        } {
            if(max-h[i]>=2) {
                System.out.println("No");
                return;
            }
            max = Math.max(max, h[i]);
        } if(max-h[i]>=2) {
                System.out.println("No");
                return;
            } max-h[i]>=2 max-h[i] max h[i] h i 2 {
                System.out.println("No");
                return;
            } System.out.println("No") System.out.println System.out System System.out "No" return; max = Math.max(max, h[i]) max Math.max(max, h[i]) Math.max Math max h[i] h i System.out.println("Yes") System.out.println System.out System System.out "Yes" String[] args args
import java.util.*;
class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] h = new int[n];
        for(int i = 0; i<n; i++) {
            h[i] = sc.nextInt();
        }
        int max = h[0];
        for(int i = 1; i<n; i++) {
            if(max-h[i]>=2) {
                System.out.println("No");
                return;
            }
            max = Math.max(max, h[i]);
        }
        System.out.println("Yes");

    }
}