#include <iostream>

#include <cstdio>

#include <cstring>

#include <cstdlib>

#include <cmath>

#include <algorithm>

using namespace std;

const int MaxN = 100000 + 5, MaxM = 100 + 5;

inline void Read(int &Num) {

	char c; c = getchar();

	while (c < '0' || c > '9') c = getchar();

	Num = c - '0'; c = getchar();

	while (c >= '0' && c <= '9') {

		Num = Num * 10 + c - '0';

		c = getchar();

	}

}

inline int gmax(int a, int b) {return a > b ? a : b;}

int n, m, Ans;

int A[MaxN], f[3][MaxM][3];

int main()

{

	Read(n); Read(m);

	for (int i = 1; i <= n; ++i) Read(A[i]);

	int Now = 0, Last = 1;

	m = m * 2 - 1;

	Ans = 0;

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

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

			f[Now][j][0] = gmax(f[Last][j][0], f[Last][j - 1][1]);

			f[Now][j][1] = gmax(f[Last][j][1], f[Last][j - 1][0]);

			if (A[i] == 0) ++f[Now][j][0];

			else ++f[Now][j][1];

			Ans = gmax(Ans, f[Now][j][0]);

			Ans = gmax(Ans, f[Now][j][1]);

		}

		Now ^= 1; Last ^= 1;

	}

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

	return 0;

}