package quki.algorithm.dp;

import java.util.Scanner;

public class BOJ2240 {

public static void main(String[] args) {

Scanner sc = new Scanner(System.in);

int n = sc.nextInt();

int m = sc.nextInt();

int a[] = new int[n + 1];

int d[][] = new int[n + 1][m + 1];

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

a[i] = sc.nextInt();

}

// ÃʱâÈ­ ÀÛ¾÷

if (a[1] == 1) {

d[1][0] = 1;

} else {

d[1][1] = 1;

}

for (int i = 2; i <= n; i++) {

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

if (j == 0) {

d[i][j] = d[i - 1][j];

} else {

d[i][j] = Math.max(d[i - 1][j - 1], d[i - 1][j]);

}

if ((j % 2 == 0 && a[i] == 1) || (j % 2 == 1 && a[i] == 2)) {

d[i][j]++;

}

}

}

int max = 0;

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

max = Math.max(max, d[n][i]);

}

System.out.println(max);

}

}