#include<iostream>

#include<cstdio>

#include<cstring>

#include<algorithm>

using namespace std;

#define MAXN 2100

#define INF 0x3f3f3f3f

int dp[MAXN][MAXN];

int g[MAXN][MAXN];

int c[MAXN],sum[MAXN];

int main()

{

        freopen("input.txt","r",stdin);

        //freopen("output.txt","w",stdout);

        int i,j,k,n,m;

        int x,y,z;

        scanf("%d",&n);

        for (i=;i<=n;i++)

        {

                scanf("%d",c+i);

        }

        for (i=n;i>=;i--)

                sum[i]=sum[i+]+c[i];

        for (i=;i<MAXN;i++)

                for (j=;j<MAXN;j++)

                        dp[i][j]=g[i][j]=-INF;

        for (i=;i<=n;i++)

        {

                dp[n-i+][i]=sum[n-i+];

                for (j=i;j<=n;j++)

                {

                        g[n-i+][j]=sum[n-i+];

                }

        }

        for (i=n;i>=;i--)

        {

                for (j=;i+j<=n;j++)

                {

                        if (g[i+j][min(j*,n)]==-INF)continue;

                        dp[i][j]=sum[i]-g[i+j][min(j*,n-i)];

                        g[i][j]=max(g[i][j-],dp[i][j]);

                }

        }

        cout<<max(dp[][],dp[][])<<endl;

}