// Problem: G. Game of Questions
// Contest: Codeforces - 2022-2023 ICPC, NERC, Northern Eurasia Onsite (Unrated, Online Mirror, ICPC Rules, Teams Preferred)
// URL: https://codeforces.com/problemset/problem/1773/G
// Memory Limit: 1024 MB
// Time Limit: 5000 ms
// 
// Powered by CP Editor (https://cpeditor.org)

// 私は猫です

#include<bits/stdc++.h>
#define ull unsigned long long
#define ll long long
#define pb push_back
#define mkp make_pair
#define fi first
#define se second
#define inf 1000000000
#define infll 1000000000000000000ll
#define pii pair<int,int>
#define rep(i,a,b,c) for(int i=(a);i<=(b);i+=(c))
#define per(i,a,b,c) for(int i=(a);i>=(b);i-=(c))
#define F(i,a,b) for(int i=a,i##end=b;i<=i##end;i++)
#define dF(i,a,b) for(int i=a,i##end=b;i>=i##end;i--)
#define cmh(sjy) while(sjy--)
#define lowbit(x) (x&(-x))
#define HH printf("\n")
#define eb emplace_back
#define poly vector<int>
#define SZ(x) ((int)x.size())
using namespace std;
template<typename T>inline void chkmax(T &x,const T &y){ x=std::max(x,y); }
template<typename T>inline void chkmin(T &x,const T &y){ x=std::min(x,y); }
const int mod=998244353,maxn=500005;
int n,zsy,mx,c1[maxn],c2[maxn],sum[maxn],c[maxn];
double f[maxn],dp[maxn],g[maxn];
void FMT(double *f,int op){
	F(i,0,n-1)F(s,0,mx)if((s>>i)&1){
		if(op>0)f[s^(1<<i)]+=f[s];
		else f[s^(1<<i)]-=f[s];
	}
}
void solve(){
	cin>>zsy>>n,dp[mx=(1<<n)-1]=1;
	F(_,1,zsy){
		string str; cin>>str;
		int s=0; F(i,0,n-1)if(str[i]=='1')s^=(1<<i);
		++c1[s],++c2[mx^s],++c[s],f[s]+=1;
	} FMT(f,1);
	double ans=0;
	F(i,0,n-1)F(s,0,mx)if((s>>i)&1)c1[s]+=c1[s^(1<<i)],c2[s]+=c2[s^(1<<i)];
	dF(i,n,1){
		F(s,0,mx)g[s]=0;
		F(s,0,mx)if(__builtin_popcount(s)==i){
			const int num=zsy-c1[mx^s]-c2[mx^s];
			if(num)g[s]=dp[s]/num;
			if(!num&&(s&1))ans+=dp[s];
		} FMT(g,1);
		F(s,0,mx)g[s]*=f[s];
		FMT(g,-1);
		F(s,1,mx)if(__builtin_popcount(s)<i)dp[s]+=g[s];
	}
	cout<<fixed<<setprecision(12)<<ans;
}
signed main(){
	ios::sync_with_stdio(0),cin.tie(0),cout.tie(0);
	int zsy=1;
	F(____,1,zsy)solve();
}