POJ 2385 Apple Catching

#include <iostream>
#include <cstring>
using namespace std;

int dp[1001][31];
int a[1001];

int main()
{
    int n,s;
    int res;
    
    while(cin>>n>>s)
    {
        memset(dp,0,sizeof(dp));    
        for(int i=1;i<=n;i++)
        {
            cin>>a[i];
            for(int j = 0;j<=s;j++)
            {
                if((s-j) % 2 +1 ==a[i])
                {
                    if(j==0)
                        dp[i][j] = dp[i-1][j]+1;
                    else
                        dp[i][j] = max(dp[i-1][j]+1,dp[i-1][j-1]);
                }
                else 
                {
                    if(j==0)
                        dp[i][j] = dp[i-1][j];
                    else
                        dp[i][j] = max(dp[i-1][j],dp[i-1][j-1]+1);
                }
            }
        }
        res = 0;
        for(int i=0;i<=s;i++)
        {
            res = res>dp[n][i]?res:dp[n][i];
        }
        
        cout<<res<<endl;
    }
    return 0;
}