#include <cstdio>

#define Nmax 303
#define Mmax 303
#define precizie 1000
#define ll long long

int N, M, R, C, Amax;
int A[Nmax][Mmax];
int S[Nmax][Mmax];
ll v[Mmax];
int i,j;

void citire()
{
 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][M+j] = A[i+N][j] = A[i+N][j+M] = A[i][j];
         Amax = Amax > A[i][j] ? Amax : A[i][j];
        }
}

void compute()
{
 for (i=1; i<=2*N; ++i)
     for (j=1; j<=2*M; ++j)
         S[i][j] = S[i-1][j] + A[i][j];
}

int exista(int V)
{
 int st,dr,k;
 ll dif;
 for (i=0; i<=N-1; ++i)
     for (j=i+R; j<=i+N; ++j)
         {
          st=1;
          dr=C;
          dif = (ll) V*(j-i);
          for (k=1; k<=M+C; ++k)
              v[k] = v[k-1] + (ll) (S[j][k] - S[i][k]) * precizie - dif;                                        
          if (v[dr]>=0) return 1;                              
          while (dr<M+C)
                {
                 ++dr;                 
                 if (dr-st>=M)
                         ++st;
                 while (dr-st>=C && v[st-1] > v[st] )
                        ++st;
                 if (v[dr]-v[st-1]>=0) return 1;
                }
         }
 return 0;
}

void cauta()
{
 int p=1, nr=0;
 Amax *= precizie;
 while ((p << 1)<=Amax) p<<=1;
 while (p)
       {
        if (exista(nr+p)) nr+=p;
        p>>=1;
        while (nr+p>Amax) p>>=1;
       }
 printf("%d.%03d\n",nr/1000,nr%1000);
}

int main()
{
 citire();
 compute();
 freopen("balans.out","w",stdout);
 cauta();
 fclose(stdout);
 return 0;
}