C++ :

#define MAXN 1010UL

#define lson l,mid,t
#define rson mid+1,r,t|1

#include <cstdio>

int n,m,m4,A,B,C,D,s[MAXN][MAXN],ml,mr,Ans,posl,posr;

inline int MIN(int a,int b){
	return a<b?a:b;
}

inline int in(){
	int x=0,c=getchar();
	while(c<'0'||c>'9') c=getchar();
	for(;c>='0'&&c<='9';c=getchar()) x=(x<<1)+(x<<3)+c-48;
	return x;
}

inline int Martix(int x,int y){
	if(x<C||y<D) return 0x1fffffff;
	return s[x][y]-s[x-C][y]-s[x][y-D]+s[x-C][y-D];
}

inline int Martix_Biger(int x,int y){
	return s[x][y]-s[x-A][y]-s[x][y-B]+s[x-A][y-B];
}

struct SegTree{
	int id,tr[MAXN<<2],pl,pr;
	inline void s_Build(int l,int r,int rt){
		if(l==r){tr[rt]=Martix(id,l);return;}
		int mid=(l+r)>>1,t=rt<<1;
		s_Build(lson);s_Build(rson);
		tr[rt]=MIN(tr[t],tr[t|1]);
		return;
	}
	inline int s_QUERY(int l,int r){
		pl=l,pr=r;return s_Query(1,m,1);
	}
	inline int s_Query(int l,int r,int rt){
		if(pl<=l&&pr>=r) return tr[rt];
		int mid=(l+r)>>1,t=rt<<1,rtn=0x2fffffff;
		if(pl<=mid) rtn=s_Query(lson);
		if(pr>mid){
			int temp=s_Query(rson);
			if(temp<rtn) rtn=temp;
		}
		return rtn;
	}
	friend SegTree operator + (const SegTree a,const SegTree b){
		SegTree c;
		for(int i=1;i<=m4;i++) c.tr[i]=MIN(a.tr[i],b.tr[i]);
		return c;
	}
}tree[MAXN<<2];

inline void Build(int l,int r,int rt){
	if(l==r){
		tree[rt].id=l;
		tree[rt].s_Build(1,m,1);
		return;
	}
	int mid=(l+r)>>1,t=rt<<1;
	Build(lson);Build(rson);
	tree[rt]=tree[t]+tree[t|1];
	return;
}

inline int Query(int l,int r,int rt){
	if(posl<=l&&posr>=r){
		return tree[rt].s_QUERY(ml,mr);
	}
	int mid=(l+r)>>1,t=rt<<1,rtn=0x2fffffff;
	if(posl<=mid) rtn=Query(lson);
	if(posr>mid){
		int temp=Query(rson);
		if(temp<rtn) rtn=temp;
	}
	return rtn;
}

int main(){
	scanf("%d%d%d%d%d%d",&n,&m,&A,&B,&C,&D);m4=m*3;
	for(int i=1;i<=n;i++) for(int j=1;j<=m;j++) s[i][j]=in(),s[i][j]+=s[i][j-1];
	for(int i=1;i<=n;i++) for(int j=1;j<=m;j++) s[i][j]+=s[i-1][j];
	Build(1,n,1);
	for(int i=A;i<=n;i++){
		posl=i-A+1+C;posr=i-1;
		for(int j=B;j<=m;j++){
			ml=j-B+1+D;mr=j-1;
			int p=Martix_Biger(i,j)-Query(1,n,1);
			if(p>Ans) Ans=p;
		}
	}
	printf("%d\n",Ans);
	return 0;
}