#include<iostream>

 #include<cstring>

 #include<cstdio>

 #include<cmath>

 #include<algorithm>

 using namespace std;

 const int N=;

 int n,m,x[N],sa[N],c[N],k,height[N],rk[N],y[N],ans,q[N],head,tail,s[N];

 void get_sa(){

     for(int i=;i<=n;i++)c[x[i]=s[i]]++;

     for(int i=;i<=m;i++)c[i]+=c[i-];

     for(int i=n;i>=;i--)sa[c[x[i]]--]=i;

     for(int k=;k<=n;k<<=){

         int num=;

         for(int i=n-k+;i<=n;i++)y[++num]=i;

         for(int i=;i<=n;i++)if(sa[i]>k)y[++num]=sa[i]-k;

         for(int i=;i<=m;i++)c[i]=;

         for(int i=;i<=n;i++)c[x[i]]++;

         for(int i=;i<=m;i++)c[i]+=c[i-];

         for(int i=n;i>=;i--)sa[c[x[y[i]]]--]=y[i],y[i]=;

         for(int i=;i<=n;i++){

             swap(x[i],y[i]);

         }

         x[sa[]]=;num=;

         for(int i=;i<=n;i++){

             x[sa[i]]=(y[sa[i]]==y[sa[i-]]&&y[sa[i]+k]==y[sa[i-]+k])?num:++num;

         }

         if(n==num)break;

         m=num;

     }

 }

 void get_height(){

     for(int i=;i<=n;i++)rk[sa[i]]=i;

     int k=;

     for(int i=;i<=n;i++){

         if(rk[i]==)continue;

         if(k)k--;

         int j=sa[rk[i]-];

         while(j+k<=n&&i+k<=n&&s[j+k]==s[i+k])k++;

         height[rk[i]]=k;

     }

 }

 int main(){

     scanf("%d%d",&n,&k);

     if(k==){

         printf("%d",n);

         return ;

     }

     m=;

     for(int i=;i<=n;i++){

         scanf("%d",&s[i]);

     }

     get_sa();

     get_height();

     head=;tail=;

     for(int i=;i<=k;i++){

         while(height[i]<=height[q[tail]]&&head<=tail)tail--;

         q[++tail]=i;

     }

     ans=height[q[head]];

     for(int i=k+;i<=n;i++){

         while(q[head]<=i-k+&&head<=tail)head++;

         while(height[i]<=height[q[tail]]&&head<=tail)tail--;

         q[++tail]=i;

         ans=max(ans,height[q[head]]);

     }

     printf("%d",ans);

     return ;

 }