#include<bits/stdc++.h>
#define FILE "read"
#define MAXN 510
#define eps 1e-6
#define INF 1e9
using namespace std;
struct node{int y,next,rel;double v;}e[MAXN*MAXN*2];
int n,m,S,T,len,sum,a[MAXN],b[MAXN],Map[MAXN][MAXN],level[MAXN],Link[MAXN];
queue<int>q;
inline int read(){
	int x=0,f=1;  char ch=getchar();
	while(!isdigit(ch))  {if(ch=='-')  f=-1;  ch=getchar();}
	while(isdigit(ch))  {x=x*10+ch-'0';  ch=getchar();}
	return x*f;
}
void insert(int x,int y,double v){
	e[++len].next=Link[x];Link[x]=len;e[len].y=y;e[len].v=v;e[len].rel=len+1;
	e[++len].next=Link[y];Link[y]=len;e[len].y=x;e[len].v=0;e[len].rel=len-1;
}
bool bfs(){
	memset(level,-1,sizeof(level));
	q.push(S);  level[S]=0;
	while(!q.empty()){
		int x=q.front();  q.pop();
		for(int i=Link[x];i;i=e[i].next)
			if(level[e[i].y]==-1&&e[i].v>eps){
				q.push(e[i].y);
				level[e[i].y]=level[x]+1;
			}
	}
	return level[T]>=0;
}
double MAXFLOW(int x,double flow){
	if(x==T)  return flow;
	double maxflow=0,d=0;
	for(int i=Link[x];i&&maxflow-flow<eps;i=e[i].next)
		if(level[e[i].y]==level[x]+1&&e[i].v>eps)
			if((d=MAXFLOW(e[i].y,min(e[i].v,flow-maxflow)))>eps)
				e[i].v-=d,e[e[i].rel].v+=d,maxflow+=d;
	if(maxflow<eps)  level[x]=-1;
	return maxflow;
}
void pre(){len=0;memset(Link,0,sizeof(Link));}
bool check(double x){
	S=0;  T=n+m+1;  pre();
	for(int i=1;i<=n;++i)  insert(i+m,T,(double)a[i]);
	for(int i=1;i<=m;++i)  insert(S,i,(double)x*b[i]);
	for(int i=1;i<=m;++i)for(int j=1;j<=n;++j)if(Map[i][j]) insert(i,j+m,INF);
	double d=0,ans=0;
	while(bfs()) while((d=MAXFLOW(S,INF))>eps)  ans+=d;
	return fabs(sum-ans)<eps;
}
int main(){
	freopen(FILE".in","r",stdin);
	freopen(FILE".out","w",stdout);
	n=read();  m=read();
	for(int i=1;i<=n;++i)  a[i]=read(),sum+=a[i];
	for(int i=1;i<=m;++i)  b[i]=read();
	for(int i=1;i<=m;++i)for(int j=1;j<=n;++j)Map[i][j]=read();
	double l=0,r=INF;
	while(l+eps<r){
		double mid=(l+r)/2;
		if(check(mid))  r=mid;
		else l=mid;
	}
	printf("%.6lf\n",check(l)?l:r);
	return 0;
}