//minamoto

 #include<bits/stdc++.h>

 using namespace std;

 #define getc() (p1==p2&&(p2=(p1=buf)+fread(buf,1,1<<21,stdin),p1==p2)?EOF:*p1++)

 char buf[<<],*p1=buf,*p2=buf;

 template<class T>inline bool cmin(T&a,const T&b){return a>b?a=b,:;}

 template<class T>inline bool cmax(T&a,const T&b){return a<b?a=b,:;}

 inline int read(){

     #define num ch-'0'

     char ch;bool flag=;int res;

     while(!isdigit(ch=getc()))

     (ch=='-')&&(flag=true);

     for(res=num;isdigit(ch=getc());res=res*+num);

     (flag)&&(res=-res);

     #undef num

     return res;

 }

 const int N=;

 int sum[N][N],sum1[N][N],sum2[N][N],q[N],mn[N][N];

 int n,m,A,B,C,D,h,t,res;

 void init(){

     for(int i=C+;i<n;++i){

         h=,t=;

         for(int j=D+;j<m;++j){

             while(h<=t&&sum2[i][q[t]]>=sum2[i][j]) --t;

             q[++t]=j;

             if(q[h]<=j-B+D+) ++h;

             mn[i][j]=sum2[i][q[h]];

         }

     }

 }

 void solve(){

     for(int j=D+;j<m;++j){

         h=,t=;

         for(int i=C+;i<n;++i){

             while(h<=t&&mn[q[t]][j]>=mn[i][j]) --t;

             q[++t]=i;

             if(q[h]<=i-A+C+) ++h;

             cmax(res,sum1[i+][j+]-mn[q[h]][j]);

         }

     }

 }

 int main(){

 //    freopen("testdata.in","r",stdin);

     n=read(),m=read(),A=read(),B=read(),C=read(),D=read();

     if(n==||m==) return puts(""),;

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

     sum[i][j]=read()+sum[i-][j]+sum[i][j-]-sum[i-][j-];

     for(int i=A;i<=n;++i) for(int j=B;j<=m;++j)

     sum1[i][j]=sum[i][j]-sum[i-A][j]-sum[i][j-B]+sum[i-A][j-B];

     for(int i=C;i<=n;++i) for(int j=D;j<=m;++j)

     sum2[i][j]=sum[i][j]-sum[i-C][j]-sum[i][j-D]+sum[i-C][j-D];

     init(),solve();

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

     return ;

 }