#include <fstream>
#include <iomanip>
#include <cmath>
using namespace std;

const int MAX_D = 151;
const double MAX_AVG = 15000000.;
const double EPS = 0.0001;
const double INF = 1.e50;

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

int M, N, R, C;
int A[MAX_D << 1][MAX_D << 1];
int S[MAX_D << 1];
double T[MAX_D << 1];
double balans = 0.;

void read() {
    in >> M >> N >> R >> C;
    for(int i = 1; i <= M; ++i)
        for(int j = 1; j <= N; ++j) {
            in >> A[i][j];
            A[i + M][j] = A[i][j + N] = A[i + M][j + N] = A[i][j];
        }
    for(int i = 1; i <= 2 * M; ++i)
        for(int j = 1; j <= 2 * N; ++j)
            A[i][j] += A[i - 1][j];
}

double max_sum(double X) {
    for(int i = 1; i <= 2 * N; ++i)
        T[i] = T[i - 1] + S[i] - X;
    double sum = -INF, t = INF;
    for(int i = C; i <= 2 * N; ++i) {
        t = min(t, T[i - C]);
        sum = max(sum, T[i] - t);
    }
    return sum;
}

double binary_search(double lo, double hi) {
    double X = max_sum((lo + hi) / 2.);
    if(fabs(X) < EPS)
        return (lo + hi) / 2.;
    if(X < 0.)
        return binary_search(lo, (lo + hi) / 2.);
    else
        return binary_search((lo + hi) / 2., hi);
}

void solve() {
    if(!R) ++R;
    if(!C) ++C;
    for(; R <= M; ++R)
        for(int i = 1; i <= M; ++i) {
            for(int j = 1; j <= 2 * N; ++j)
                S[j] = A[i + R - 1][j] - A[i - 1][j];
            balans = max(balans, binary_search(1, MAX_AVG) / R);
        }
}


int main() {
    read();
    solve();
    out << fixed << setprecision(3) << floor(balans * 1000.) / 1000. << "\n";
    return 0;
}