#include<cstdio>

#include<algorithm>

#include<cstring>

using namespace std;

const int maxn=;

int n,m,s[maxn],x[maxn],y[maxn],base[maxn],sa[maxn],h[maxn],K,q[maxn];

struct lshs{int ord,num;}lsh[maxn];

bool cmp(lshs a,lshs b)

{return a.num<b.num;}

void build_sa(int m)

{

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

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

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

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

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

     {

         int p=;

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

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

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

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

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

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

         swap(x,y);

         p=;x[sa[]]=;

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

          x[sa[i]]=y[sa[i]]==y[sa[i-]]&&y[sa[i]+k]==y[sa[i-]+k]?p:++p;

         if(p>=n)break;

         m=p;

     }

    int k=;

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

     {

         if(k)k--;

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

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

         h[x[i]]=k;

     }

}

int main()

{

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

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

     {

         scanf("%d",&lsh[i].num);

         lsh[i].ord=i;

     }

    sort(lsh+,lsh+n+,cmp);

    int p=;s[lsh[].ord]=;

    for(int i=;i<=n;i++)s[lsh[i].ord]=lsh[i].num==lsh[i-].num?p:++p;

    build_sa(p);

    K--;

    int head=,tail=;

    int ans=;

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

     {

         while(h[q[tail-]]>h[i]&&tail>head)tail--;

         q[tail++]=i;

         if(i-q[head]>=K)head++;

         if(i>=K+)ans=max(ans,h[q[head]]);

     }

    printf("%d",ans);

    return ;

}