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/*
luogu1004
多进程DP 
*/
#include<iostream>
#include<cstdio>
#include<cstring>
#include<cstdlib>
using namespace std;
template<typename T>
T Max(const T& a,const T& b){return a>b?a:b;}
template<typename T>
void read(T& w)
{
	char r;int f=1;
	for(r=getchar();(r<48||r>57)&&r!='-';r=getchar());
	if(r=='-')r=getchar(),f=-1;
	for(w=0;r>=48&&r<=57;r=getchar())w=w*10+r-48;
	w*=f;
}
const int maxn=13;
int n;
int a[maxn][maxn];
void input()
{
	read(n);
	int x,y,z;
	for(read(x),read(y),read(z);x||y||z;read(x),read(y),read(z))
	{
		a[x][y]=z;
	}
}

int f[maxn][maxn][maxn][maxn];
void dp()
{
	for(int i=1;i<=n;++i) for(int j=1;j<=n;++j)
	{
		for(int k=1;k<=n;++k) for(int l=1;l<=n;++l)
		{
			f[i][j][k][l]
			=Max(
				Max(
					f[i-1][j][k-1][l],f[i-1][j][k][l-1]),
				Max(
					f[i][j-1][k-1][l],f[i][j-1][k][l-1])
				);
			f[i][j][k][l]+=a[i][j];
			if(i!=k||j!=l)
				f[i][j][k][l]+=a[k][l];
			//cout<<f[i][j][k][l]<<" ";
		}
	}
}
int main()
{
	freopen("luogu1004_1.in","r",stdin);
	//freopen("luogu1004.out","w",stdout);
	input();
	dp();
	printf("%d\n",f[n][n][n][n]);
	return 0;
}

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/*
luogu1006
多进程DP 
*/
#include<iostream>
#include<cstdio>
#include<cstring>
#include<cstdlib>
using namespace std;
template<typename T>
T Max(const T& a,const T& b){return a>b?a:b;}
template<typename T>
void read(T& w)
{
	char r;int f=1;
	for(r=getchar();(r<48||r>57)&&r!='-';r=getchar());
	if(r=='-')r=getchar(),f=-1;
	for(w=0;r>=48&&r<=57;r=getchar())w=w*10+r-48;
	w*=f;
}
const int maxn=53;
int n,m;
int a[maxn][maxn];
void input()
{
	read(n),read(m);
	for(int i=1;i<=n;++i)
	{
		for(int j=1;j<=m;++j)
		{
			read(a[i][j]);
		}
	}
}

int f[maxn][maxn][maxn][maxn];
void dp()
{
	for(int i=1;i<=n;++i) for(int j=1;j<=m;++j)
	{
		for(int k=1;k<=n;++k) for(int l=1;l<=m;++l)
		{
			f[i][j][k][l]
			=Max(
				Max(
					f[i-1][j][k-1][l],f[i-1][j][k][l-1]),
				Max(
					f[i][j-1][k-1][l],f[i][j-1][k][l-1])
				);
			f[i][j][k][l]+=a[i][j];
			if(i!=k||j!=l)
				f[i][j][k][l]+=a[k][l];
			//cout<<f[i][j][k][l]<<" ";
		}
	}
}
int main()
{
	freopen("luogu1006_1.in","r",stdin);
	//freopen("luogu1006.out","w",stdout);	
	input();
	dp();
	printf("%d\n",f[n][m][n][m]);
	return 0;
}

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template<typename T>
void Swap(T& a,T& b){T t=a;a=b;b=t;}

template<typename T>
void shift(T* ary,int k,int f,bool comp(const T& a,const T&b) )
{
	for(int son=k*2;son<=f;k=son,son=k*2)
	{
		if(son+1<=f&&comp(ary[son+1],ary[son]))
			++son;
		if(comp(ary[son],ary[k]))
			Swap(ary[son],ary[k]);
		else break;
	}
}

template<typename T>
void heapSort(T* ary,int l,int r,bool comp(const T& a,const T&b))//r不是超尾而是最后一个元素 
{
	int mid=(l+r)/2;
	for(int i=mid;i>=l;--i)
		shift(ary,i,r,comp);
	for(int i=r;i>=l+1;--i)
	{
		Swap(ary[i],ary[l]);
		shift(ary,l,i-1,comp);
	}
}

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template<typename T,int maxnode>
struct QUE
{
	T ary[maxnode];
	int f,t;
	int cnt;
	QUE(){f=t=cnt=0;}
	void clear(){f=t=cnt=0;}
	bool empty(){return cnt==0;}
	void push(const T& w)//if t+1!=f
	{
		ary[t++]=w;
		if(t==maxnode)t=0;
		++cnt;
	}
	T front(){return ary[f];}
	void pop()
	{
		++f;
		if(f==maxnode)f=0;
		--cnt;
	}
};