#include <bits/stdc++.h>
using namespace std;
bool identical(vector<int>v,int k){
map<int,int>m;
for(int i=0;i<v.size();i++){
for(int j=i+1;j<v.size();j++){
if(v[i]==v[j] && j-i<=k)return true;
}
}
return false;
}
int main() {
// your code goes here
int n;cin>>n;
vector<int>v(n);
for(int i=0;i<n;i++)cin>>v[i];
int k;cin>>k;
if(identical(v,k)){
cout<<"YES"<<endl;
}else{
cout<<"NO"<<endl;
}
return 0;
}
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