/*by SilverN*/

 #include<algorithm>

 #include<iostream>

 #include<cstring>

 #include<cstdio>

 #include<cmath>

 #include<vector>

 using namespace std;

 const int mxn=;

 int read(){

     int x=,f=;char ch=getchar();

     while(ch<'' || ch>''){if(ch=='-')f=-;ch=getchar();}

     while(ch>='' && ch<=''){x=x*+ch-'';ch=getchar();}

     return x*f;

 }

 int f[mxn];

 int a[mxn];

 int n;

 int main(){

     int i,j;

     while(scanf("%d",&n)!=EOF){

         for(i=;i<=n;i++){

             f[i]=;

             a[i]=read();

             for(j=;j<i;j++)

                 if(a[j]>=a[i])f[i]=max(f[i],f[j]+);

         }

         bool flag=;

         for(i=;i<=n;i++)

             if(f[i]>){printf("No!\n");flag=;break;}

         if(!flag)continue;

         printf("Yes!\n");

     }

     return ;

 }