#include <fstream>
#include <algorithm>
using namespace std;
ifstream cin("euclid.in");
ofstream cout("euclid.out");
int R[10][10][401][401], E[401];
int main()
{
    int t,n,m,h,w;
    cin>>t;
    for(int i = 2;i<=400;i++)
        E[i] = E[i/2] + 1;
    for(int testcase = 1;testcase<=t;testcase++)
    {
        cin>>n>>m>>h>>w;
        for(int i = 1;i<=n;i++)
            for(int j = 1;j<=m;j++)
                cin>>R[0][0][i][j];
        for(int q = 0; (1<<q)<= n; q++)
            for(int p = 0;(1<<p)<=m;p++)
                for(int i = 1;i<=n;i++)
                    for(int j = 1;j<=m;j++)
                    {
                        int f1 = i + (1<<(max(q-1,0)));
                        int f2 = j + (1<<(max(p-1,0)));
                        R[q][p][i][j] = R[max(q-1,0)][max(p-1,0)][i][j];
                        if(f1<=n)
                            R[q][p][i][j] = __gcd(R[q][p][i][j],R[(q-1,0)][max(q-1,0)][f1][j]);
                        if(f2<=m)
                            R[q][p][i][j] = __gcd(R[q][p][i][j],R[max(q-1,0)][max(p-1,0)][i][f2]);
                        if(f1<=n&&f2<=m)
                            R[q][p][i][j] = __gcd(R[q][p][i][j],R[max(q-1,0)][max(p-1,0)][f1][f2]);
                    }
        int sol = -1e9;
        for(int i = 1;i<=n-h+1;i++)
            for(int j = 1;j<=m-w+1;j++)
            {
                int e1 = E[h];
                int e2 = E[w];
                int len1 = (1<<e1);
                int len2 = (1<<e2);
                int val1 = R[e1][e2][i][j];
                int val2 = R[e1][e2][i+h-len1][j];
                int val3 = R[e1][e2][i][j+w-len2];
                int val4 = R[e1][e2][i+h-len1][j+w-len2];
                int current = __gcd(__gcd(val1,val2),__gcd(val3,val4));
                sol = max(sol,current);
            }
        cout<<"Case #"<<testcase<<": "<<sol<<'\n';
    }
    return 0;
}