#include <iostream>
#include <algorithm>
#include <math.h>
#include <cstdio>
#include <string.h>
#include <string>
using namespace std;
int n;
int a[501];
bool mid_search(int x){
int l = 0,r = n - 1;
while(r - l >= 0){
int mid = (l+r)/2;
if(a[mid] == x) return true;
else if(a[mid] > x) r = mid - 1;
else l = mid + 1;
}
return false;
}
int main(){
cin>>n;
for(int i=0;i<n;i++){
cin>>a[i];
}
sort(a,a+n);
int x;
cin>>x;
if(mid_search(x)){
cout<<"yes"<<endl;
}
else{
cout<<"no"<<endl;
}
return 0;
}