#include <stdio.h>
#define NMAX 305
#define ll long long
int n,m,p,q,A[NMAX][NMAX];
ll S[NMAX][NMAX],C[NMAX],D[NMAX],E[NMAX];
void read()
{
	scanf("%d%d%d%d",&n,&m,&p,&q);
	int i,j;
	for (i=1; i<=n; i++)
	{
		for (j=1; j<=m; j++)
			scanf("%d",&A[i][j]);
		for (j=m+1; j<2*m; j++)
			A[i][j]=A[i][j-m];
	}
	for (i=n+1; i<2*n; i++)
		for (j=1; j<2*m; j++)
			A[i][j]=A[i-n][j];
	n=2*n-1; m=2*m-1;
	for (i=1; i<=n; i++)
		for (j=1; j<=m; j++)
		{
			A[i][j]*=10000;
			S[i][j]=S[i-1][j]+A[i][j];
		}
}
inline ll min(ll x,ll y)
{
	return x<y ? x : y;
}
bool ok(int val)
{
	int i,j,k;
	for (i=1; i<=n-p+1; i++)
		for (j=i+p-1; j<=n; j++)
		{
			for (k=1; k<=m; k++)
				C[k]=(S[j][k]-S[i-1][k])-(ll)val*(j-i+1);
			for (k=1; k<=m; k++)
			{
				E[k]=E[k-1]+C[k];
				D[k]=min(D[k-1],E[k]);
				if (k>=q)
					if (E[k]-D[k-q]>0)
						return 1;
			}
		}
	return 0;
}
ll cbin()
{
	ll i,step=(1<<30);
	for (i=0; step; step>>=1)
		if (ok(i+step))
			i+=step;
	return i;
}
int main()
{
	freopen("balans.in","r",stdin);
	freopen("balans.out","w",stdout);
	read();
	ll ans=cbin();
	printf("%lld.%lld\n",ans/10000,(ans%10000)/10);
	return 0;
}