#include <bits/stdc++.h>

using namespace std;

ifstream fin("balans.in");
ofstream fout("balans.out");

const int nmax = 305;
int n, m, r, c, mat[nmax][nmax];
double mat2[nmax][nmax], sum[nmax], sum2[nmax];

bool Check(double ans){
    for (int i = 1; i <= n; ++i){
        for (int j = 1; j <= m; ++j){
            mat2[i][j] = mat[i][j] - ans;
        }
    }
    for (int row = 1; row <= n; ++row){
        memset(sum, 0, sizeof sum);
        for (int row2 = row; row2 <= n; ++row2){
            for (int j = 1; j <= m; ++j){
                sum[j] += mat2[row2][j];
            }
            if (row2 - row + 1 >= r){
                for (int j = 1; j <= m; ++j){
                    sum2[j] = sum[j] + sum2[j - 1];
                }
                deque <int> dq;
                for (int j = 1; j <= m; ++j){
                    if (j >= c){
                        while (dq.size() > 0 && sum2[dq.back()] > sum2[j - c]) dq.pop_back();
                        dq.push_back(j - c);
                        if (sum2[j] - sum2[dq.front()] >= 0){
                            return true;
                        }
                    }
                }
            }
        }
    }
    return false;
}

int main(){
    fin >> n >> m >> r >> c;
    for (int i = 1; i <= n; ++i){
        for (int j = 1; j <= m; ++j){
            fin >> mat[i][j];
            int x = mat[i][j];
            mat[i + n][j] = x;
            mat[i][j + m] = x;
            mat[i + n][j + m] = x;
        }
    }
    n = n + n;
    m = m + m;
    double st = 0, dr = 100000, ans;
    for (int i = 1; i <= 30; ++i){
        double mid = (st + dr) / 2;
        if (Check(mid)){
            st = mid;
            ans = mid;
        }
        else{
            dr = mid;
        }
    }
    fout << fixed << setprecision(3) << ans;
    return 0;
}