#include <iostream>

 #include <cstdio>

 #include <cstring>

 using namespace std;

 int t,w,x[];

 int dp[][][];

 int dfs(int now,int cur,int rem)

 {

     if(dp[now][cur][rem] != -)

         return dp[now][cur][rem];

     if(now == t)

         return ;

     int p = dfs(now + ,cur,rem) + (cur == x[now] - );

     if(rem >= )

         p = max(p, dfs(now, - cur,rem - ) + (cur == x[now] - ));

     return dp[now][cur][rem] = p;

 }

 int main()

 {

     memset(dp,-,sizeof(dp));

     cin >> t >> w;

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

     {

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

     }

     cout << dfs(,,w) << endl;

     return ;

 }