import java.util.Scanner;
import java.util.HashMap;
import java.util.List;
import java.util.Arrays;
import java.util.ArrayList;
import java.lang.Math;

public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] h = new int[n];
        int[] hl = new int[n];
        for (int i = 0; i < n; i++) {
            h[i] = sc.nextInt();
            hl[i] = 0;
        }
        for (int i = 0; i < n-1; i++) {
            if (h[i] > h[i+1]) {
                h[i] -= 1;
                hl[i] = 1;
                if (i != 0) {
                    for (int j = i; j >= 1; j--) {
                        if (h[j-1] > h[j]) {
                            if (hl[j-1] != 0) {
                                System.out.println("No");
                                System.exit(0);
                            } else {
                                if (h[j-1] - h[j] > 1) {
                                    System.out.println("No");
                                    System.exit(0);
                                } else {
                                    h[j-1] -= 1;
                                    hl[j-1] = 1;
                                }
                            }
                        }
                    }
                }
            }
        }
        System.out.println("Yes");
    }

} import java.util.Scanner; Scanner java.util import java.util.HashMap; HashMap java.util import java.util.List; List java.util import java.util.Arrays; Arrays java.util import java.util.ArrayList; ArrayList java.util import java.lang.Math; Math java.lang public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] h = new int[n];
        int[] hl = new int[n];
        for (int i = 0; i < n; i++) {
            h[i] = sc.nextInt();
            hl[i] = 0;
        }
        for (int i = 0; i < n-1; i++) {
            if (h[i] > h[i+1]) {
                h[i] -= 1;
                hl[i] = 1;
                if (i != 0) {
                    for (int j = i; j >= 1; j--) {
                        if (h[j-1] > h[j]) {
                            if (hl[j-1] != 0) {
                                System.out.println("No");
                                System.exit(0);
                            } else {
                                if (h[j-1] - h[j] > 1) {
                                    System.out.println("No");
                                    System.exit(0);
                                } else {
                                    h[j-1] -= 1;
                                    hl[j-1] = 1;
                                }
                            }
                        }
                    }
                }
            }
        }
        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];
        int[] hl = new int[n];
        for (int i = 0; i < n; i++) {
            h[i] = sc.nextInt();
            hl[i] = 0;
        }
        for (int i = 0; i < n-1; i++) {
            if (h[i] > h[i+1]) {
                h[i] -= 1;
                hl[i] = 1;
                if (i != 0) {
                    for (int j = i; j >= 1; j--) {
                        if (h[j-1] > h[j]) {
                            if (hl[j-1] != 0) {
                                System.out.println("No");
                                System.exit(0);
                            } else {
                                if (h[j-1] - h[j] > 1) {
                                    System.out.println("No");
                                    System.exit(0);
                                } else {
                                    h[j-1] -= 1;
                                    hl[j-1] = 1;
                                }
                            }
                        }
                    }
                }
            }
        }
        System.out.println("Yes");
    } main {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] h = new int[n];
        int[] hl = new int[n];
        for (int i = 0; i < n; i++) {
            h[i] = sc.nextInt();
            hl[i] = 0;
        }
        for (int i = 0; i < n-1; i++) {
            if (h[i] > h[i+1]) {
                h[i] -= 1;
                hl[i] = 1;
                if (i != 0) {
                    for (int j = i; j >= 1; j--) {
                        if (h[j-1] > h[j]) {
                            if (hl[j-1] != 0) {
                                System.out.println("No");
                                System.exit(0);
                            } else {
                                if (h[j-1] - h[j] > 1) {
                                    System.out.println("No");
                                    System.exit(0);
                                } else {
                                    h[j-1] -= 1;
                                    hl[j-1] = 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[] h = new int[n]; h new int[n] n int[] hl = new int[n]; hl new int[n] n for (int i = 0; i < n; i++) {
            h[i] = sc.nextInt();
            hl[i] = 0;
        } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
            h[i] = sc.nextInt();
            hl[i] = 0;
        } {
            h[i] = sc.nextInt();
            hl[i] = 0;
        } h[i] = sc.nextInt() h[i] h i sc.nextInt() sc.nextInt sc hl[i] = 0 hl[i] hl i 0 for (int i = 0; i < n-1; i++) {
            if (h[i] > h[i+1]) {
                h[i] -= 1;
                hl[i] = 1;
                if (i != 0) {
                    for (int j = i; j >= 1; j--) {
                        if (h[j-1] > h[j]) {
                            if (hl[j-1] != 0) {
                                System.out.println("No");
                                System.exit(0);
                            } else {
                                if (h[j-1] - h[j] > 1) {
                                    System.out.println("No");
                                    System.exit(0);
                                } else {
                                    h[j-1] -= 1;
                                    hl[j-1] = 1;
                                }
                            }
                        }
                    }
                }
            }
        } 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;
                hl[i] = 1;
                if (i != 0) {
                    for (int j = i; j >= 1; j--) {
                        if (h[j-1] > h[j]) {
                            if (hl[j-1] != 0) {
                                System.out.println("No");
                                System.exit(0);
                            } else {
                                if (h[j-1] - h[j] > 1) {
                                    System.out.println("No");
                                    System.exit(0);
                                } else {
                                    h[j-1] -= 1;
                                    hl[j-1] = 1;
                                }
                            }
                        }
                    }
                }
            }
        } {
            if (h[i] > h[i+1]) {
                h[i] -= 1;
                hl[i] = 1;
                if (i != 0) {
                    for (int j = i; j >= 1; j--) {
                        if (h[j-1] > h[j]) {
                            if (hl[j-1] != 0) {
                                System.out.println("No");
                                System.exit(0);
                            } else {
                                if (h[j-1] - h[j] > 1) {
                                    System.out.println("No");
                                    System.exit(0);
                                } else {
                                    h[j-1] -= 1;
                                    hl[j-1] = 1;
                                }
                            }
                        }
                    }
                }
            }
        } if (h[i] > h[i+1]) {
                h[i] -= 1;
                hl[i] = 1;
                if (i != 0) {
                    for (int j = i; j >= 1; j--) {
                        if (h[j-1] > h[j]) {
                            if (hl[j-1] != 0) {
                                System.out.println("No");
                                System.exit(0);
                            } else {
                                if (h[j-1] - h[j] > 1) {
                                    System.out.println("No");
                                    System.exit(0);
                                } else {
                                    h[j-1] -= 1;
                                    hl[j-1] = 1;
                                }
                            }
                        }
                    }
                }
            } h[i] > h[i+1] h[i] h i h[i+1] h i+1 i 1 {
                h[i] -= 1;
                hl[i] = 1;
                if (i != 0) {
                    for (int j = i; j >= 1; j--) {
                        if (h[j-1] > h[j]) {
                            if (hl[j-1] != 0) {
                                System.out.println("No");
                                System.exit(0);
                            } else {
                                if (h[j-1] - h[j] > 1) {
                                    System.out.println("No");
                                    System.exit(0);
                                } else {
                                    h[j-1] -= 1;
                                    hl[j-1] = 1;
                                }
                            }
                        }
                    }
                }
            } h[i] -= 1 h[i] h i 1 hl[i] = 1 hl[i] hl i 1 if (i != 0) {
                    for (int j = i; j >= 1; j--) {
                        if (h[j-1] > h[j]) {
                            if (hl[j-1] != 0) {
                                System.out.println("No");
                                System.exit(0);
                            } else {
                                if (h[j-1] - h[j] > 1) {
                                    System.out.println("No");
                                    System.exit(0);
                                } else {
                                    h[j-1] -= 1;
                                    hl[j-1] = 1;
                                }
                            }
                        }
                    }
                } i != 0 i 0 {
                    for (int j = i; j >= 1; j--) {
                        if (h[j-1] > h[j]) {
                            if (hl[j-1] != 0) {
                                System.out.println("No");
                                System.exit(0);
                            } else {
                                if (h[j-1] - h[j] > 1) {
                                    System.out.println("No");
                                    System.exit(0);
                                } else {
                                    h[j-1] -= 1;
                                    hl[j-1] = 1;
                                }
                            }
                        }
                    }
                } for (int j = i; j >= 1; j--) {
                        if (h[j-1] > h[j]) {
                            if (hl[j-1] != 0) {
                                System.out.println("No");
                                System.exit(0);
                            } else {
                                if (h[j-1] - h[j] > 1) {
                                    System.out.println("No");
                                    System.exit(0);
                                } else {
                                    h[j-1] -= 1;
                                    hl[j-1] = 1;
                                }
                            }
                        }
                    } int j = i; int j = i; j i j >= 1 j 1 j-- j-- j {
                        if (h[j-1] > h[j]) {
                            if (hl[j-1] != 0) {
                                System.out.println("No");
                                System.exit(0);
                            } else {
                                if (h[j-1] - h[j] > 1) {
                                    System.out.println("No");
                                    System.exit(0);
                                } else {
                                    h[j-1] -= 1;
                                    hl[j-1] = 1;
                                }
                            }
                        }
                    } {
                        if (h[j-1] > h[j]) {
                            if (hl[j-1] != 0) {
                                System.out.println("No");
                                System.exit(0);
                            } else {
                                if (h[j-1] - h[j] > 1) {
                                    System.out.println("No");
                                    System.exit(0);
                                } else {
                                    h[j-1] -= 1;
                                    hl[j-1] = 1;
                                }
                            }
                        }
                    } if (h[j-1] > h[j]) {
                            if (hl[j-1] != 0) {
                                System.out.println("No");
                                System.exit(0);
                            } else {
                                if (h[j-1] - h[j] > 1) {
                                    System.out.println("No");
                                    System.exit(0);
                                } else {
                                    h[j-1] -= 1;
                                    hl[j-1] = 1;
                                }
                            }
                        } h[j-1] > h[j] h[j-1] h j-1 j 1 h[j] h j {
                            if (hl[j-1] != 0) {
                                System.out.println("No");
                                System.exit(0);
                            } else {
                                if (h[j-1] - h[j] > 1) {
                                    System.out.println("No");
                                    System.exit(0);
                                } else {
                                    h[j-1] -= 1;
                                    hl[j-1] = 1;
                                }
                            }
                        } if (hl[j-1] != 0) {
                                System.out.println("No");
                                System.exit(0);
                            } else {
                                if (h[j-1] - h[j] > 1) {
                                    System.out.println("No");
                                    System.exit(0);
                                } else {
                                    h[j-1] -= 1;
                                    hl[j-1] = 1;
                                }
                            } hl[j-1] != 0 hl[j-1] hl j-1 j 1 0 {
                                System.out.println("No");
                                System.exit(0);
                            } System.out.println("No") System.out.println System.out System System.out "No" System.exit(0) System.exit System 0 {
                                if (h[j-1] - h[j] > 1) {
                                    System.out.println("No");
                                    System.exit(0);
                                } else {
                                    h[j-1] -= 1;
                                    hl[j-1] = 1;
                                }
                            } if (h[j-1] - h[j] > 1) {
                                    System.out.println("No");
                                    System.exit(0);
                                } else {
                                    h[j-1] -= 1;
                                    hl[j-1] = 1;
                                } h[j-1] - h[j] > 1 h[j-1] - h[j] h[j-1] h j-1 j 1 h[j] h j 1 {
                                    System.out.println("No");
                                    System.exit(0);
                                } System.out.println("No") System.out.println System.out System System.out "No" System.exit(0) System.exit System 0 {
                                    h[j-1] -= 1;
                                    hl[j-1] = 1;
                                } h[j-1] -= 1 h[j-1] h j-1 j 1 1 hl[j-1] = 1 hl[j-1] hl j-1 j 1 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) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] h = new int[n];
        int[] hl = new int[n];
        for (int i = 0; i < n; i++) {
            h[i] = sc.nextInt();
            hl[i] = 0;
        }
        for (int i = 0; i < n-1; i++) {
            if (h[i] > h[i+1]) {
                h[i] -= 1;
                hl[i] = 1;
                if (i != 0) {
                    for (int j = i; j >= 1; j--) {
                        if (h[j-1] > h[j]) {
                            if (hl[j-1] != 0) {
                                System.out.println("No");
                                System.exit(0);
                            } else {
                                if (h[j-1] - h[j] > 1) {
                                    System.out.println("No");
                                    System.exit(0);
                                } else {
                                    h[j-1] -= 1;
                                    hl[j-1] = 1;
                                }
                            }
                        }
                    }
                }
            }
        }
        System.out.println("Yes");
    }

} public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] h = new int[n];
        int[] hl = new int[n];
        for (int i = 0; i < n; i++) {
            h[i] = sc.nextInt();
            hl[i] = 0;
        }
        for (int i = 0; i < n-1; i++) {
            if (h[i] > h[i+1]) {
                h[i] -= 1;
                hl[i] = 1;
                if (i != 0) {
                    for (int j = i; j >= 1; j--) {
                        if (h[j-1] > h[j]) {
                            if (hl[j-1] != 0) {
                                System.out.println("No");
                                System.exit(0);
                            } else {
                                if (h[j-1] - h[j] > 1) {
                                    System.out.println("No");
                                    System.exit(0);
                                } else {
                                    h[j-1] -= 1;
                                    hl[j-1] = 1;
                                }
                            }
                        }
                    }
                }
            }
        }
        System.out.println("Yes");
    }

} Main
import java.util.Scanner;
import java.util.HashMap;
import java.util.List;
import java.util.Arrays;
import java.util.ArrayList;
import java.lang.Math;

public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] h = new int[n];
        int[] hl = new int[n];
        for (int i = 0; i < n; i++) {
            h[i] = sc.nextInt();
            hl[i] = 0;
        }
        for (int i = 0; i < n-1; i++) {
            if (h[i] > h[i+1]) {
                h[i] -= 1;
                hl[i] = 1;
                if (i != 0) {
                    for (int j = i; j >= 1; j--) {
                        if (h[j-1] > h[j]) {
                            if (hl[j-1] != 0) {
                                System.out.println("No");
                                System.exit(0);
                            } else {
                                if (h[j-1] - h[j] > 1) {
                                    System.out.println("No");
                                    System.exit(0);
                                } else {
                                    h[j-1] -= 1;
                                    hl[j-1] = 1;
                                }
                            }
                        }
                    }
                }
            }
        }
        System.out.println("Yes");
    }

}
