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