/* package whatever; // don't place package name! */
import java.util.*;
import java.lang.*;
import java.io.*;
/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
{
Scanner sc
=new Scanner
(System.
in); int k=sc.nextInt();
int n=sc.nextInt();
int arr[]=new int[n];
for(int i=0;i<n;i++){
arr[i]=sc.nextInt();
}
HashMap
<Integer,Integer
>hm
=new HashMap
<>(); for(int i=0;i<n;i++){
if(hm.containsKey(arr[i])){
int idx=i-hm.get(arr[i]);
if(idx<=k){
return ;
}
}
hm.put(arr[i],i);
}
}
}
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