#include<iostream>

#include<cstdio>

#include<cstring>

#include<set>

using namespace std;

int x[]={ , ,-, };

int y[]={ ,-, , };

int lable[][],d[][];

int T,m,n,p,q,deepth=,cake=;

void dfs(int a,int b)

{

    if(d[a][b]>deepth||a<||a>=m||b<||b>=n||lable[a][b]==){return;}

    lable[a][b]=;

    cake++;

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

    {

        if(a+x[i]<||a+x[i]>=m||b+y[i]<||b+y[i]>=n){continue;}

        dfs(a+x[i],b+y[i]);

    }

    return;

}

void solve()

{

    int i,j;

    for(i=; i<m; i++)

    {

        if(lable[i][]==)

        {

            continue;

        }

        dfs(i,);

    }

    for(i=; i<m; i++)

    {

        if(lable[i][n-]==)

        {

            continue;

        }

        dfs(i,n-);

    }

    for(j=; j<n; j++)

    {

        if(lable[][j]==)

        {

            continue;

        }

        dfs(,j);

    }

    for(j=; j<n; j++)

    {

        if(lable[m-][j]==)

        {

            continue;

        }

        dfs(m-,j);

    }

}

int main()

{

    int i,j;

    scanf("%d",&T);

    while(T--)

    {

        scanf("%d%d%d%d",&m,&n,&p,&q);

        set<int>donser;

        for(i=;i<m;i++)

        {

            for(j=;j<n;j++)

            {

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

                donser.insert(d[i][j]);

            }

        }

        while()

        {

            deepth=*donser.begin();

            solve();

            donser.erase(deepth);

            if(cake>=p&&cake<=q)

            {

                cout<<deepth<<endl;

                cake=;

                memset(lable,,sizeof(lable));

                memset(d,,sizeof(d));

                break;

            }

            if(donser.size()==||cake>q)

            {

                cout<<"-1"<<endl;

                cake=;

                memset(lable,,sizeof(lable));

                memset(d,,sizeof(d));

                break;

            }

            cake=;

            memset(lable,,sizeof(lable));

        }

    }

    return ;

}