#include <cstdio>

#define Nmax 302

int i, n, r, l, m, N, M, Vmax, p, u, mij, sol, j, c, Vmin;
int a[Nmax][Nmax], d[Nmax];
long long INF, Sum, v[Nmax], S[Nmax][Nmax], Q;

int cont(int X){
	
	int p, u;
	Sum = - INF;
	for (i = 1; i <= n; i++)
		for (j = i + r - 1; j - i + 1 <= n; j++) {
			
			Q = (long long)X * (long long)(j - i + 1);
			for (l = 1; l <= M; l++) {
				v[l] = S[j][l] - S[i-1][l] - Q;
				v[l]+= v[l-1];
			}
			
			p = u = 1; d[1] = 1;
			for (l = 2; l + c <= M; l++) {
				
				while ( p <= u && l - d[p] >= m - c + 1 ) p++;
				while ( p <= u && v[l] <= v[ d[u] ] ) u--;
				d[++u] = l;
				
				if( Sum < v[l + c] - v[ d[p] ] ) Sum = v[l + c] - v[ d[p] ]; 
				
			}
		}
	
	if( Sum >= 0 ) return 1;
	return 0;
	
}

int main(){

	FILE *f = fopen("balans.in", "r");
	FILE *g = fopen("balans.out", "w");
	
	fscanf(f,"%d %d %d %d", &n, &m, &r, &c); Vmin = 100000001;
	for (i = 1; i <= n; i++)
		for(j = 1; j <= m; j++){
			fscanf(f,"%d", &a[i][j]);
			a[i][j]*= 1000;
			if(a[i][j] > Vmax) Vmax = a[i][j];
			if(a[i][j] < Vmin ) Vmin = a[i][j];
		}
	
	N = n << 1; M = m << 1;
	for (i = 1; i <= n; i++)
		for(j = 1; j <= m; j++)
			a[i][j+m] = a[i][j];
	
	for (i = 1; i <= n; i++)
		for (j = 1; j <= M; j++)
			a[i + n][j] = a[i][j];
	
	for (i = 1; i <= N; i++)
		for (j = 1; j <= M; j++)
			S[i][j] = S[i-1][j] + (long long)a[i][j];
	
	p = Vmin; u = Vmax; INF = 1 << 30; INF*= 1000;
	while ( p <= u ) {
		
		mij = (p + u) >> 1;
		if (cont(mij)){
			sol = mij;
			p = mij + 1;
		}
		
		else
			u = mij - 1;
		
	}
	
	fprintf (g,"%.3lf", (double)sol / (double)1000);
	
	fclose (f);
	fclose (g);
	
	return 0;

}