import java.util.*;
public class test {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
Deque deque = new ArrayDeque();
int n = in.nextInt();
int m = in.nextInt();
int a[]=new int[10000001];
int max=0,u=0;
for (int i = 0; i < n; i++) {
int num = in.nextInt();
if(deque.size()max)
max=u;
if(a[(int)deque.removeFirst()]--==1)
u--;
deque.addLast(num);
if(a[num]++==0)
u++;
}
}
if(u>max)
max=u;
System.out.println(max);
}
}