import java.util.*;

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

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