#include<stdio.h>
int n,m,r,c,i,j,a[301][301],b[301][301],sc,sol;
void read(),solve();
int main()
{
	read();
	solve();
	return 0;
}
void read()
{
	freopen("balans.in","r",stdin);
	freopen("balans.out","w",stdout);
	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]);
}
void solve()
{
	for(i=1;i<=n;i++)
		for(j=1;j<c;j++)
			a[i][j+m]=a[i][j];
	m=m+c-1;
	for(i=1;i<r;i++)
		for(j=1;j<=m;j++)
			a[i+n][j]=a[i][j];
	n=n+r-1;
	for(i=1;i<=n;i++)
		for(j=1;j<=m;j++)
			b[i][j]=a[i][j]+b[i-1][j]+b[i][j-1]-b[i-1][j-1];
	sol=b[r][c];
	for(i=r;i<=n;i++)
		for(j=c;j<=m;j++)
		{
			sc=b[i][j]-b[i-r][j]-b[i][j-c]+b[i-r][j-c];
			sol=(sc>sol)?sc:sol;
		}
	printf("%.3lf",(double)sol/(double)(r*c));
}