#include <cstdio>#include <cstring>#include <vector>using namespace std;const int N=1000010,M=1000010;int n,rank[N],sa[N],h[N],tmp[N],cnt[N],ans;int s[N];void suffixarray(int n,int m){    int i,j,k;n++;    for(i=0;i<2*n+5;i++)rank[i]=sa[i]=h[i]=tmp[i]=0;    for(i=0;i<m;i++)cnt[i]=0;    for(i=0;i<n;i++)cnt[rank[i]=s[i]]++;    for(i=1;i<m;i++)cnt[i]+=cnt[i-1];    for(i=0;i<n;i++)sa[--cnt[rank[i]]]=i;    for(k=1;k<=n;k<<=1){        for(i=0;i<n;i++){            j=sa[i]-k;            if(j<0)j+=n;            tmp[cnt[rank[j]]++]=j;        }sa[tmp[cnt[0]=0]]=j=0;        for(i=1;i<n;i++){            if(rank[tmp[i]]!=rank[tmp[i-1]]||rank[tmp[i]+k]!=rank[tmp[i-1]+k])cnt[++j]=i;            sa[tmp[i]]=j;        }memcpy(rank,sa,n*sizeof(int));        memcpy(sa,tmp,n*sizeof(int));        if(j>=n-1)break;    }for(j=rank[h[i=k=0]=0];i<n-1;i++,k++)    while(~k&&s[i]!=s[sa[j-1]+k])h[j]=k--,j=rank[sa[j]+1];}vector<int> v[N]; int k; bool check(int x){    int cnt=-1;    for(int i=1;i<=n;i++){        if(h[i]<x)v[++cnt].clear();        v[cnt].push_back(i);    }for(int i=0;i<=cnt;i++)if(v[i].size()>=k)return 1;    return 0;}int main(){    while(~scanf("%d%d",&n,&k)){        for(int i=0;i<n;i++)scanf("%d",&s[i]);        suffixarray(n,M);        int l=0,r=n,ans=0;        while(l<=r){            int mid=(l+r)>>1;            if(check(mid))ans=mid,l=mid+1;            else r=mid-1;        }printf("%d\n",ans);    }return 0;}