#include<bits/stdc++.h>

using namespace std;

#define setIO(s) freopen(s".in","r",stdin)

#define maxn 1002

#define inf 1000000000

deque<int>q;

int n,m,A,B,C,D;

int minv[maxn][maxn],sumv[maxn][maxn],val[maxn][maxn],tot[maxn][maxn];

int main()

{

    // setIO("input");

    scanf("%d%d%d%d%d%d",&n,&m,&A,&B,&C,&D);

    for(int i=1;i<=n;++i)

    {

        for(int j=1;j<=m;++j)

        {

            scanf("%d",&sumv[i][j]);

            sumv[i][j]+=(sumv[i][j-1]+sumv[i-1][j]-sumv[i-1][j-1]);

        }

    }

    for(int i=1;i<=n;++i)

    {

        for(int j=1;j<=m;++j)

        {

            if(i>=A&&j>=B) tot[i][j]=sumv[i][j]-sumv[i-A][j]-sumv[i][j-B]+sumv[i-A][j-B];

            if(i>=C&&j>=D) val[i][j]=sumv[i][j]-sumv[i-C][j]-sumv[i][j-D]+sumv[i-C][j-D];

        }

    }

    for(int j=1;j<=m;++j)

    {

        while(!q.empty()) q.pop_front();

        for(int i=2;i<=n;++i)

        {

            while(!q.empty()&&i-q.front()+1>=A-C) q.pop_front();

            if(!val[i-1][j]) { minv[i][j]=inf; continue; }

            while(!q.empty()&&val[i-1][j]<=val[q.back()][j]) q.pop_back();

            q.push_back(i-1);

            minv[i][j]=val[q.front()][j];

        }

    }

    int ans=0;

    for(int i=1;i<=n;++i)

    {

        while(!q.empty()) q.pop_front();

        for(int j=2;j<=m;++j)

        {

            while(!q.empty()&&j-q.front()+1>=B-D) q.pop_front();

            if(!val[i][j-1]) continue;

            while(!q.empty()&&minv[i][j-1]<=minv[i][q.back()]) q.pop_back();

            q.push_back(j-1);

            ans=max(ans, tot[i][j]-minv[i][q.front()]);

        }

    }

    printf("%d\n",ans);

    return 0;

}