#include <iostream>
#include <cstdio>
#define MAXN 164
#define MAXM 164

using namespace std;

int a[2*MAXN][2*MAXM];
int pre[2*MAXN][2*MAXN];
int n, m, r, c;

void citire()
{
	scanf("%d %d %d %d", &n, &m, &r, &c);
    for (int i = 1; i <= n; i++)
		for (int j = 1; j <= m; j++) {
			scanf("%d", &a[i][j]);
			a[i][j+m] = a[i+n][j] = a[i+n][j+m] = a[i][j];
		}
	for (int i = 1; i <= 2*n; i++)
		for (int j = 1; j <= 2*m; j++)
			pre[i][j] = pre[i-1][j] + a[i][j];

}

int check(int stx, int len, double k)
{
    double crt[2*MAXM];
    int deck[2*MAXM];
    crt[0] = 0;
    for (int i = 1; i <= m; i++)
        crt[i] = crt[i-1] + pre[stx+len-1][i] - pre[stx-1][i] - (k*len);
    double val = 0;
    if (crt[c] > 0) return 1;
    int st = 0, dr = -1;
    for (int i = c+1; i <= m; i++) {
        while (st <= dr && crt[i-c] < crt[deck[dr]])
			dr--;
		deck[++dr] = i-c;
        while (i-deck[st] > m)
			st++;
        double scad = crt[deck[st]];
        if (crt[i]-scad >= 0) return 1;
    }
    return 0;
}

void solve()
{
    double rez = -1;
    for (int i = 1; i <= 2*n-r+1; i++)
		for (int j = r; i+j-1 <= 2*n; j++) {
			double k, lo = 0, hi = 1000000;
			while (hi - lo > 0.00008) {
				k = (lo + hi) / 2;
				if (check(i, j, k))
					lo = k;
				else
					hi = k;
			}
			if (lo > rez)
				rez = lo;
		}
	printf("%.3lf", rez);
}

int main()
{
    freopen("balans.in", "r", stdin);
    freopen("balans.out", "w", stdout);

    citire();
    solve();

	return 0;
}