import java.util.Scanner;

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