#include<cstdio>
#include<algorithm>
#include<cstring>
#include<iostream>
#include<vector>
#include<set>
#include<map>
#include<bitset>

#define ls (t<<1)
#define rs ((t<<1)+1)
#define mid ((l+r)>>1)
#define fi first
#define se second
#define mk make_pair

#define N 1005
#define M 200005
#define seed 23333
#define Mo 998244353

using namespace std;
int i,j,m,n,p,k,a[N][N],sum[N];
double f[N],len[N],ans,prob[N][N];
int main()
{ 
   while (scanf("%d%d",&n,&m)!=EOF)
   {
         memset(sum,0,sizeof(sum));
         ans=0;
         for (i=1;i<=n;++i)
         {
           for (j=1;j<=m;++j) scanf("%d",&a[i][j]),sum[i]+=a[i][j];
         }
         for (i=1;i<=n;++i)
           for (j=1;j<=m;++j) prob[i][j]=1.*a[i][j]/sum[i];
         for (i=1;i<=m;++i)
         {
               memset(f,0,sizeof(f));
               memset(len,0,sizeof(len));
               for (j=1;j<=n;++j)
               {
                    f[j]=f[j-1]+prob[j][i]*(2*len[j-1]+1);
                    //len[j]=prob[j][i]*(len[j-1]+1);
                    len[j]=len[j-1]+prob[j][i];
               }
               ans+=f[n];
         }
         printf("%.2lf\n",ans);
   }
}