import java.util.Scanner;

public class Main {

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

}
