#include <cstdio>
#include <queue>
using namespace std;
#define MAX_N 310
#define f first
#define s second
#define mp make_pair

int A[MAX_N][MAX_N];
double B[MAX_N][MAX_N], S[MAX_N];
int i,j,k,l,n,m,r,c;
double st,dr, mx;

double max(double a, double b) { return a<b?b:a; }
typedef pair<double, int> di;

struct comp {
	bool operator()(di A, di B) { 
		return A.f > B.f;
	}
};

int valid( double x ) {
	for ( i=1; i<=n; ++i ) 
		for ( j=1; j<=m; ++j ) 
			B[i][j] = B[i-1][j] + A[i][j] - x;
	for ( i=1; i<=n; ++i )
		for ( j=i+r-1; j<=n; ++j ) {
			S[0] = 0;
			for ( k=1; k<=m; ++k ) 
				S[k] = S[k-1] + B[j][k] - B[i-1][k];
			priority_queue<di, vector<di>, comp> Q;
			for ( k=c; k<=n; ++k ) {
				Q.push( mp(S[k-c], k) );
				if ( S[k]-Q.top().f>=0 ) return 1;
			}
		}
	return 0;
}

int main() {
	freopen("balans.in", "r", stdin);
	scanf("%d %d %d %d", &n, &m, &r, &c);
	for ( i=1; i<=n; ++i )
		for ( j=1; j<=m; ++j ) {
			scanf("%d", A[i]+j);
			A[i+n][j] = A[i][j+n] = A[i+n][j+n] = A[i][j];
			mx = max(mx, 1.*A[i][j]);
		}
	n *= 2, m *= 2;
	st = 0, dr = 2*mx;
	while ( st<=dr && dr-st > 0.0001 ) {
		double mij = (st+dr)/2;
		if ( valid(mij) ) 
			st = mij;
		else
			dr = mij;
	}
	fprintf(fopen("balans.out", "w"), "%.3lf\n", st);
	return 0;
}