#include <cstdio>
using namespace std;

int v[612][612];
int s[612][612];

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

  	int n, m, r, c, i, j, tmp, C;
  	double max = -1, aux;

  	scanf("%d%d%d%d", &n, &m, &r, &c);
  	C = c;

  	for(i = 1; i <= n; ++i)
   		for(j = 1; j <= m; ++j) {
     		scanf("%d",v[i]+j);
     		v[i + n][j] = v[i][j];
     		v[i][j + m] = v[i][j];
     		v[i + n][j + m] = v[i][j];
    	}

  	n <<= 1;
  	m <<= 1;

  	for(i = 1; i <= n; ++i)
   		for(j = 1; j <= m; ++j)
    		s[i][j] = s[i - 1][j] + s[i][j - 1] - s[i - 1][j - 1] + v[i][j];

  	int N = n / 2;
  	int M = m / 2;
  	for(; r <= N; ++r)
   		for(c = C; c <= M; ++c)
    		for(i = N + 1; i <= n; ++i)
     			for(j = M + 1; j <= m; ++j) {
       				aux = s[i][j] - s[i - r][j] - s[i][j - c] + s[i - r][j - c];
       				if(aux > max * (r * c))
        				max = aux / (r * c);
      			}

  	printf("%.3f\n", max - 0.000499);
  	return 0;
 }