#include<stdio.h>
#include<stdlib.h>
typedef struct node{
    int data;
    struct node *prev;
    struct node *next;
}Node;
  Node *head,*tail;
void create(int num){
    Node *newNode = (Node*)malloc(1*sizeof(Node));
    newNode->data=num;
    newNode->next=NULL;
    if(head==NULL){
        head=newNode;
        tail=newNode;
    }
    else{
        newNode->prev=tail;
        tail->next=newNode;
        tail=newNode;
    }
}
void display(){
    printf("Yes");
    
}
int main(){
    int size, num,i;
    scanf("%d",&size);
    for(i=1;i<=size;i++){
        if(!(scanf("%d",&num)){
            printf("Invalid input");
            return 0;
        }
        create (num);
    }
    display();
}