#include<iostream>
using namespace std;
int  head = 1, tail, ans = -0x3f3f3f3f, HEAD, TAIL;
int a[1003][1003], max1[1003][1003], max2[1003][1003], min1[1003][1003], min2[1003][1003], q[1003], Q[1003];
int x, m, n,y;
int main()
{
    cin >> n >> m >> x >> y;
    for ( int i = 1; i <= n; i++)
    {
        for (int j = 1; j <= m; j++)
            cin >> a[i][j];
    }
    for (int i = 1; i <= n; i++)
    {
        head = tail = q[1] = 1;
        HEAD = TAIL = Q[1] = 1;
        for (int j = 2; j <= m; j++)
        {
            while (a[i][j] >= a[i][Q[TAIL]] && HEAD <= TAIL) TAIL--;
            Q[++TAIL] = j;
            if (j - Q[HEAD] >= y) HEAD++;
        while (a[i][j] <= a[i][q[tail]] && head <= tail) tail--;
        q[++tail] = j;
        if (j - q[head] >= y) head++;
        if (j >= y) max1[i][j - y + 1] = a[i][Q[HEAD]], min1[i][j - y + 1] = a[i][q[head]];
    }
}
for (int j = 1; j <= m - y + 1; j++)
{
    head = tail = q[1] = 1;
    HEAD = TAIL = Q[1] = 1;
    for (int i = 2; i <= n; i++)
    {
        while (max1[i][j] >= max1[Q[TAIL]][j] && HEAD <= TAIL) TAIL--;
        Q[++TAIL] = i;
        if (i - Q[HEAD] >= x) HEAD++;

        while (min1[i][j] <= min1[q[tail]][j] && head <= tail) tail--;
        q[++tail] = i;
        if (i - q[head] >= x) head++;
        if (i >= x) max2[i - x + 1][j] = max1[Q[HEAD]][j], min2[i - x + 1][j] = min1[q[head]][j];
    }
}
for (int i = 1; i <= n - x + 1; i++)
{
    for (int j = 1; j <= m - y + 1; j++)
        ans = max(ans, max2[i][j] - min2[i][j]);
}
cout << ans;
return 0;

}