#include<iostream>

 #include<algorithm>

 #include<cstring>

 #include<cstdio>

 #include<vector>

 #include<stack>

 #include<queue>

 #include<cmath>

 #include<map>

 #include<set>

 using namespace std;

 typedef long long ll;

 typedef pair<int,int> pll;

 const int INF = 0x3f3f3f3f;

 const int maxn =  + ;

 int n,m;

 struct Edge

 {

     int from, to, cap, flow, cost;

     Edge(int u, int v, int c, int f, int w) :from(u), to(v), cap(c), flow(f), cost(w) {}

 };

 struct MCMF

 {

     int n, m;

     vector<Edge> edges;

     vector<int> G[maxn];

     int inq[maxn];

     int d[maxn];

     int p[maxn];

     int a[maxn];

     void init(int n)

     {

         this->n = n;

         for (int i = ; i<n; i++) G[i].clear();

         edges.clear();

     }

     void AddEdge(int from, int to, int cap, int cost)

     {

         edges.push_back(Edge(from, to, cap, , cost));

         edges.push_back(Edge(to, from, , , -cost));

         m = edges.size();

         G[from].push_back(m - );

         G[to].push_back(m - );

     }

     bool BellmanFord(int s, int t, int &flow, int & cost)

     {

         for (int i = ; i<n; i++) d[i] = INF;

         memset(inq, , sizeof(inq));

         d[s] = ; inq[s] = ; p[s] = ; a[s] = INF;

         queue<int> Q;

         Q.push(s);

         while (!Q.empty()){

             int u = Q.front(); Q.pop();

             inq[u] = ;

             for (int i = ; i<G[u].size(); i++){

                 Edge& e = edges[G[u][i]];

                 if (e.cap>e.flow && d[e.to]>d[u] + e.cost){

                     d[e.to] = d[u] + e.cost;

                     p[e.to] = G[u][i];

                     a[e.to] = min(a[u], e.cap - e.flow);

                     if (!inq[e.to]) { Q.push(e.to); inq[e.to] = ; }

                 }

             }

         }

         if (d[t] == INF) return false;

         flow += a[t];

         cost += d[t] * a[t];

         for (int u = t; u != s; u = edges[p[u]].from)

         {

             edges[p[u]].flow += a[t];

             edges[p[u] ^ ].flow -= a[t];

         }

         return true;

     }

     int MincostMaxdflow(int s, int t){

         int flow = , cost = ;

         while (BellmanFord(s, t, flow, cost));

         return cost;

     }

 }t;

 int main()

 {

     //freopen("in.txt","r",stdin);

     while(~scanf("%d%d",&m,&n))

     {

         int src=,dst=n*m+n+;

         t.init(dst+);

         for(int i=;i<=n;i++)

         {

             t.AddEdge(src,i,,);

             for(int j=;j<=m;j++)

             {

                 int x; scanf("%d",&x);

                 for(int k=;k<=n;k++)

                     t.AddEdge(i,j*n+k,,k*x);

             }

         }

         for(int j=n+;j<=m*n+n;j++)

             t.AddEdge(j,dst,,);

         int ans = t.MincostMaxdflow(src,dst);

         printf("%.2f\n",(double)ans/n);

     }

     return ;

 }