#include <fstream>
#include <iostream>
#include <cstring>
#include <deque>
#include <algorithm>
#include <numeric>
#include <limits>
#include <iterator>

#define MAX_SIZE 305

using namespace std;

static long long mat[MAX_SIZE][MAX_SIZE];

int main()
{
    int N, M, R, C;
    fstream fin("balans.in", fstream::in);
    fstream fout("balans.out", fstream::out);
    
    double flMaxBalans = 0.0;
    
    fin >> N >> M >> R >> C;
    //cout << N << " " << M << " " << R << " " << C << endl;
    
    if (R == 0)
    {
        R = 1;
    }
    if (C == 0)
    {
        C = 1;
    }
    
    for (int i=1; i<=N; ++i)
    {
        for (int j=1; j<=M; ++j)
        {
            fin >> mat[i][j];
            mat[i+N][j] = mat[i][j];
            mat[i][j+M] = mat[i][j];
            mat[i+N][j+M] = mat[i][j];
        }
    }

    /*for (int i=1; i<=2*N; ++i)
    {
        for (int j=1; j<=2*M; ++j)
        {
            cout << mat[i][j] << " ";
        }
        cout << endl;
    }*/
    
    for (int i=1; i<=2*N; ++i)
    {
        for (int j=1; j<=2*M; ++j)
        {
            mat[i][j] = mat[i][j] + mat[i-1][j] + mat[i][j-1] - mat[i-1][j-1];
        }
    }
    
    for (int r=R; r<=N; ++r)
    {
        for (int c=C; c<=M; ++c)
        {
            for (int i=N; i<=2*N; ++i)
            {
                for (int j=M; j<=2*M; ++j)
                {
                    long long sum = mat[i][j] - mat[i-r][j] - mat[i][j-c] + mat[i-r][j-c];
                    
                    flMaxBalans = max(flMaxBalans, (double)sum / (r*c));
                }
            }
        }
    }
    
    fout.precision(3);
    fout << fixed << flMaxBalans << "\n";
    
    return 0;
}