#include <fstream>
#include <iomanip>
#include <deque>
#define NM 310
#define EPS 1e-3

using namespace std;

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

int N,M,i,j,R,C;
int A[NM][NM];
int SUM[NM][NM];
deque<int> D;
double ANS=0;
double V[NM];
int l1,l2;

void Read ()
{
    f >> N >> M >> R >> C;
    for (i=1; i<=N; i++)
        for (j=1; j<=M; j++)
        {
            f >> A[i][j];
            A[i+N][j]=A[i][j];
            A[i][j+M]=A[i][j];
            A[i+N][j+M]=A[i][j];
        }
    N<<=1;
    M<<=1;
    for (i=1; i<=N; i++)
        for (j=1; j<=M; j++)
            SUM[i][j]=SUM[i-1][j]+A[i][j];

    f.close();
}

bool Check (double X)
{
    for (l1=1; l1<=N>>1; l1++)
        for (l2=l1+R-1; l2<=N; l2++)
        {
            D.clear();
            for (j=1; j<=M; j++)
            {
                V[j]=V[j-1]+1.0*(SUM[l2][j]-SUM[l1-1][j])-X*(l2-l1+1);
                while (!D.empty() && V[j-1]<=V[D.back()]) D.pop_back();
                while (!D.empty() && j-D.front()>C) D.pop_front();
                D.push_back(j-1);
                if (V[j]-V[D.front()]>=0) return 1;
            }
        }
    return 0;
}

void Solve ()
{
    double P=0,U=100000,M;
    while (U-P>EPS)
    {
        M=(P+U)/2.0;
        if (Check(M))
        {
            ANS=M;
            P=M+EPS;
        }
        else
            U=M-EPS;
    }
}

void Print ()
{
    g << fixed << setprecision(3) << ANS << '\n';
    g.close();
}

int main ()
{
    Read();
    Solve();
    Print();
    return 0;
}