#include<iostream>
using namespace std;
int a[100],n=10;
struct Node{
int key;
Node *left;
Node *right;
};
bool Insert(Node *&p,int element){
if(p==NULL){
p=new Node;
p->key=element;
p->left=p->right=NULL;
return true;
}
if(element<p->key)
return Insert(p->left,element);
else return Insert(p->right,element);
}
void create(Node *&T,int n){
T=NULL;
for(int i=0;i<n;i++){
Insert(T,a[i]);
}
}
bool Search(Node *&T,int x){
Node*p=T;
while(p!=NULL&&x!=p->key){
if(x>p->key)
p=p->right;
else p=p->left;
}
if(p==NULL)
return false;
else return true;
}
bool Search_n(Node*&T,int x){
Node *p=T;
if(p==NULL)return false;
if(x==T->key)return true;
else if(x<T->key)return Search_n(T->left,x);
else return Search_n(T->right,x);}
int main(){
for (int i=0;i<n;i++)
cin>>a[i];
Node *T=NULL;
create(T,n);
Node *p=NULL;
int x;
cin>>x;
if(Search(T,x))
cout<<"yes"<<endl;
else cout<<"no"<<endl;
return 0;
}
