/**************************************************************

     Problem: 3993

     User: rausen

     Language: C++

     Result: Accepted

     Time:40 ms

     Memory:1156 kb

 ****************************************************************/

 #include <cstdio>

 #include <cstring>

 #include <algorithm>

 using namespace std;

 typedef double lf;

 const int N = ;

 const lf inf = 1e10;

 const lf eps = 1e-;

 const int M = N * N << ;

 inline int read();

 struct edge {

     int next, to;

     lf f;

     edge(int _n = , int _t = , lf _f = 0.0) : next(_n), to(_t), f(_f) {}

 } e[M];

 int n, m, S, T;

 int b[N];

 int first[N], tot = ;

 int q[N], d[N];

 inline void Add_Edges(int x, int y, lf z) {

     e[++tot] = edge(first[x], y, z), first[x] = tot;

     e[++tot] = edge(first[y], x, ), first[y] = tot;

 }

 #define y e[x].to

 #define p q[l]

 bool bfs() {

     static int l, r, x;

     memset(d, -, sizeof(d));

     d[q[] = S] = ;

     for (l = r = ; l != r + ; ++l)

         for (x = first[p]; x; x = e[x].next)

             if (!~d[y] && e[x].f > eps) {

                 d[q[++r] = y] = d[p] + ;

                 if (y == T) return ;

             }

     return ;

 }

 #undef p

 lf dfs(int p, lf lim) {

   if (p == T || !lim) return lim;

   int x;

   lf tmp, rest = lim;

   for (x = first[p]; x && rest > eps; x = e[x].next)

     if (d[y] == d[p] +  && ((tmp = min(e[x].f, rest)) > eps)) {

       rest -= (tmp = dfs(y, tmp));

       e[x].f -= tmp, e[x ^ ].f += tmp;

       if (!rest) return lim;

     }

   if (rest > eps) d[p] = -;

   return lim - rest;

 }

 inline bool check(lf t) {

     static int x;

     for (x = ; x <= tot; x += )

         e[x].f += e[x ^ ].f, e[x ^ ].f = ;

     for (x = first[S]; x; x = e[x].next)

         e[x].f = b[y - n] * t;

     while (bfs()) dfs(S, inf);

     for (x = first[T]; x; x = e[x].next)

         if (e[x ^ ].f > eps) return ;

     return ;

 }

 #undef y

 int main() {

     int i, j;

     lf l, r, mid;

     n = read(), m = read();

     S = n + m + , T = S + ;

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

         Add_Edges(i, T, read());

     for (i = ; i <= m; ++i)

         b[i] = read(), Add_Edges(S, n + i, );

     for (i = ; i <= m; ++i)

         for (j = ; j <= n; ++j)

             if (read() == ) Add_Edges(n + i, j, inf);

     l = , r = 5e6;

     while (r - l > eps) {

         mid = (l + r) / 2.0;

         if (check(mid)) r = mid;

         else l = mid;

     }

     printf("%.6lf\n", (l + r) / 2.0);

     return ;

 }

 inline int read() {

     static int x;

     static char ch;

     x = , ch = getchar();

     while (ch < '' || '' < ch)

         ch = getchar();

     while ('' <= ch && ch <= '') {

         x = x *  + ch - '';

         ch = getchar();

     }

     return x;

 }