#define _CRT_SECURE_NO_WARNINGS

#include<stdio.h>

#include<string.h>

#define LETTERS 1000005

#define MAX_ARRAY_SIZE 1000005

int gSuffixArray[MAX_ARRAY_SIZE];

int gCount[MAX_ARRAY_SIZE];

int gOrderBySecondKey[MAX_ARRAY_SIZE];

int gRank[MAX_ARRAY_SIZE];

int gFirstKeyArray[MAX_ARRAY_SIZE];

int gHeight[MAX_ARRAY_SIZE];

int gStr[MAX_ARRAY_SIZE];

int gStrLen;

bool Compare(int* arr, int a, int b, int step){

	return arr[a] == arr[b] && arr[a + step] == arr[b + step];

}

void GetStr(char* str){

	memset(gStr, 0, sizeof(gStr));

	gStrLen = strlen(str);

	for (int i = 0; i < gStrLen; i++){

		gStr[i] = str[i] - 'a' + 1;

	}

	gStr[gStrLen] = 0;

	gStrLen++;

}

//求后缀数组

void GetSuffixArray(){

	int n = gStrLen;

	memset(gCount, 0, sizeof(gCount));

	for (int i = 0; i < n; i++){

		gRank[i] = gStr[i];

		gCount[gRank[i]] ++;

	}

	int m = LETTERS;

	for (int i = 1; i < m; i++){

		gCount[i] += gCount[i - 1];

	}

	for (int i = n - 1; i >= 0; i--){

		gSuffixArray[--gCount[gRank[i]]] = i;

	}

	int step = 1;

	int *rank = gRank, *order_by_second_key = gOrderBySecondKey;

	while (step < n){

		int p = 0;

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

			order_by_second_key[p++] = i;

		}

		for (int i = 0; i < n; i++){

			if (gSuffixArray[i] >= step){

				order_by_second_key[p++] = gSuffixArray[i] - step;

			}

		}

		for (int i = 0; i < n; i++){

			gFirstKeyArray[i] = rank[order_by_second_key[i]];

		}

		for (int i = 0; i < m; i++){

			gCount[i] = 0;

		}

		for (int i = 0; i < n; i++){

			gCount[gFirstKeyArray[i]] ++;

		}

		for (int i = 1; i < m; i++){

			gCount[i] += gCount[i - 1];

		}

		for (int i = n - 1; i >= 0; i--){

			gSuffixArray[--gCount[gFirstKeyArray[i]]] = order_by_second_key[i];

		}

		int* tmp = rank; rank = order_by_second_key; order_by_second_key = tmp;

		rank[gSuffixArray[0]] = p = 0;

		for (int i = 1; i < n; i++){

			if (Compare(order_by_second_key, gSuffixArray[i], gSuffixArray[i - 1], step)){

				rank[gSuffixArray[i]] = p;

			}

			else{

				rank[gSuffixArray[i]] = ++p;

			}

		}

		m = p + 1;

		step *= 2;

	}

}

//求height数组

void GetHeight(){

	int n = gStrLen;

	for (int i = 0; i < n; i++){

		gRank[gSuffixArray[i]] = i;

	}

	int k = 0, j;

	for (int i = 0; i < n; i++){

		if (k){

			k--;

		}

		j = gSuffixArray[gRank[i] - 1];

		while (j + k < n && i + k < n&& gStr[i + k] == gStr[j + k]){

			k++;

		}

		gHeight[gRank[i]] = k;

	}

}

bool Find(int k, int len){

	int end = 1;

	int count = 0;

	while (end < gStrLen){

		count = 1;

		while (end < gStrLen && gHeight[end] >= len){

			count++;

			end++;

		}

		if (count >= k){

			return true;

		}

		end++;

	}

	return false;

}

int main(){

	int n, k;

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

	for (int i = 0; i < n; i++){

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

	}

	gStr[n] = 0;

	gStrLen = n + 1;

	if (k == 1){

		printf("%d\n", n);

		return 0;

	}

	GetSuffixArray();

	GetHeight();

	int beg = 0, end = n;

	while (beg < end){

		int mid = (beg + end) / 2;

		if (Find(k, mid)){

			beg = mid + 1;

		}

		else{

			end = mid;

		}

	}

	printf("%d\n", beg-1);

	return 0;

}