C :

#include "stdio.h"
int n,a[2000],s[4001];
int max;
int m[2000][2001];
int Max(int a,int b)
{
	if(a>b)
		return a;
	return b;
}
int main()
{
	int i,j;
	scanf("%d",&n);
	for(i=0;i<n;i++)
	{
		scanf("%d",&a[i]);
		s[i+1]=s[i]+a[i];
	}
	for(i=n;i<2*n;i++)
		s[i+1]=s[i]+a[i%n];
	for(j=1;j<n;j++)
	{
		for(i=0;i<n;i++)
			m[i][j]=Max(m[(i+1)%n][j-1],m[i][j-1])+s[i+j+1]-s[i];
	}
	max=m[0][n-1];
	for(i=0;i<n;i++)
	{
		if(max<m[i][n-1])
			max=m[i][n-1];
	}
	printf("%d\n",max);
	return 0;
}

C++ :

#include<iostream>
#include<cstring>
#include<cstdio>
using namespace std;
long long n,a[4001],sum[4001]={0},f_max[4001][4001]={0};
void init();
void work();
int my_min(int,int);
int my_max(int,int);
int main()
{
	//freopen("stone5.in","r",stdin);
	//freopen("stone5.out","w",stdout);
	init();
	work();
	return 0;	
}
void init()
{
	cin>>n;	
	for(int i=1;i<=n;i++)
	{
		cin>>a[i];
		a[i+n]=a[i];
	}
	for(int i=1;i<=2*n;i++) sum[i]=sum[i-1]+a[i];
}
void work()
{
	for(int d=2;d<=n;d++)
	{
		for(int i=1;i<=2*n-d+1;i++)
		{
			int j=i+d-1;
			//f_min[i][j]=0x7fffffff/2;
			/*for(int k=i;k<j;k++)
			{
				f_max[i][j]=my_max(f_max[i][j],f_max[i][k]+f_max[k+1][j]);
				f_min[i][j]=my_min(f_min[i][j],f_min[i][k]+f_min[k+1][j]);
				
			}*/
			f_max[i][j]=my_max(f_max[i+1][j],f_max[i][j-1])+sum[j]-sum[i-1];
			//f_min[i][j]=my_min(f_min[i+1][j],f_min[i][j-1])+sum[j]-sum[i-1];
			//cout<<d<<' '<<sum[j]-sum[i-1]<<' '<<i<<' '<<j<<' '<<f_min[i][j]<<endl;			
		}
	}
	long long tot2=0;
	//for(int i=1;i<=n;i++) tot1=my_min(tot1,f_min[i][i+n-1]);
	for(int i=1;i<=n;i++) tot2=my_max(tot2,f_max[i][i+n-1]);
	cout<<tot2<<endl;
}
int my_min(int x,int y)
{
	if(x<y)return x;
	else return y;
}
int my_max(int x,int y)
{
	if(x>y)return x;
	else return y;
}

Pascal :

program acm22948;
const maxn=4000;
var f:array[1..maxn,1..maxn] of longint;
    a,sum:array[0..maxn] of longint;
	d,i,j,k,n,min,max:longint;
begin
  fillchar(sum,sizeof(sum),0);
  readln(n);
  for i:=1 to n do
    begin
	  read(a[i]);
          a[n+i]:=a[i];
	end;
  for i:=1 to 2*n do
    sum[i]:=sum[i-1]+a[i];
    fillchar(f,sizeof(f),0);
  for d:=2 to n do
    for i:=1 to 2*n-d+1 do
      begin
        j:=i+d-1;
         if f[i,i]+f[i+1,j]<f[i,j-1]+f[j,j]
         then max:=f[i,j-1]+f[j,j] else max:=f[i,i]+f[i+1,j];
	  f[i,j]:=max+sum[j]-sum[i-1];
      end;
   max:=0;
   for i:=1 to n do
    if max<f[i,i+n-1] then max:=f[i,i+n-1];
   writeln(max);
end.