#include <iostream>
#include <fstream>
#include <deque>
#include <iomanip>

using namespace std;

const int Nmax = 151;

int N, M, R, C;

deque <int> deck;

double A[Nmax][Nmax];
double V[Nmax][Nmax];
double sum[Nmax][Nmax];
double sume_coloana[Nmax];
double sumCol[Nmax];

int valid( double cost )
{
    double maxim = -10000000;

    for ( int i = 1; i <= 2 * N; ++i )
    {
        for ( int j = 1; j <= 2 * M; ++j )
        {
            V[i][j] = A[i][j] - cost;
            sum[i][j] = sum[i - 1][j] + V[i][j];
        }
    }

    for ( int i = 1; i <= 2 * N; ++i )
    {
        for ( int j = i + R - 1; j - i < N && j <= 2 * N; ++j )
        {
            for ( int k = 1; k <= 2 * M; ++k )
            {
                sume_coloana[k] = sum[j][k] - sum[i - 1][k];
                sumCol[k] = sumCol[k - 1] + sume_coloana[k];
            }

            /// intre C-M
            deck.clear();

            for ( int k = C; k <= 2 * M; ++k )
            {
                while ( deck.size() && sumCol[ deck.back() ] > sumCol[k - C] ) deck.pop_back();
                while ( deck.size() && deck.front() < k - M ) deck.pop_front();

                deck.push_back( k - C );

                maxim = max( maxim, sumCol[k] - sumCol[ deck.front() ] );
            }
        }
    }

    return ( maxim >= 0 );
}

double cautare_binara()
{
    double st = 0;
    double dr = 15;
    double sol = 0;
    double m;

    while ( dr - st > 0.0001 )
    {
        m = ( st + dr ) / 2.0;

        if ( valid( m ) )
        {
            st = m;
            sol = m;
        }
        else
        {
            dr = m;
        }
    }

    return sol;
}

int main()
{
    ifstream f("balans.in");
    ofstream g("balans.out");

    f >> N >> M >> R >> C;

    for ( int i = 1; i <= N; ++i )
            for ( int j = 1; j <= M; ++j )
            {
                f >> A[i][j];
                A[i + N][j] = A[i][j + M] = A[i + N][j + M] = A[i][j];
            }

    g << fixed << setprecision( 3 );
    g << cautare_binara();

    return 0;
}