#include <fstream>
#include <iomanip>

using namespace std;

const int NMAX = 155;

int n, m, r, c;
int mat[2 * NMAX][2 * NMAX];

double s_part[2 * NMAX];
bool exists (double x) {
    int j, k;
    double sum;

    for (int i = 1; i <= 2 * n; ++ i) {
        for (k = 1; k <= 2 * m; ++ k)
            s_part[k] = 0;

        for (j = i; j <= 2 * n && j <= i + n - 1; ++ j) {
            sum = 0;
            for (k = 1; k <= 2 * m; ++ k) {
                sum += (mat[j][k] - x);
                s_part[k] += sum;
            }

            if (j < i + r - 1)
                continue ;

            sum = 0;
            for (k = c; k <= 2 * m; ++ k) {
                if (s_part[k - c] < sum)
                    sum = s_part[k - c];
                if (s_part[k] - sum >= 0)
                    return true;
            }
        }
    }

    return false;
}

int main()
{
    ifstream cin("balans.in");
    ofstream cout("balans.out");

    cin >> n >> m >> r >> c;

    int j;
    for (int i = 1; i <= n; ++ i)
        for (j = 1; j <= m; ++ j)
            cin >> mat[i][j];

    for (int i = 1; i <= 2 * n; ++ i)
        for (j = 1; j <= 2 * m; ++ j)
            mat[i][j] = mat[(i - 1) % n + 1][(j - 1) % m + 1];

    double st = -200000;
    double dr = 200000;
    double mijl;

    for (int steps = 0; steps < 100; ++ steps) {
        mijl = (st + dr) * 0.5;

        if (exists(mijl))
            st = mijl;
        else
            dr = mijl;
    }

    cout << fixed << setprecision(3) << st << '\n';

    cin.close();
    cout.close();
    return 0;
}