#include <bits/stdc++.h>
using namespace std;

struct zt_bs{
	int zt;
	int bs;
};

int n,m;
int k[101][11];

bool f[2048];
queue<zt_bs>q;
int now;

int main(){
	cin>>n>>m;
	for(int i=1;i<=m;i++)
	for(int j=1;j<=n;j++)
	cin>>k[i][j];
	
	f[(1<<n)-1]=1;
	q.push( (zt_bs) {(1<<n)-1,0} );
	
	while(!q.empty()){
		int fz=q.front().zt;
		int fb=q.front().bs;
		q.pop();
		if(fz==0){
			cout<<fb<<endl;
			return 0;
		}
		for(int i=1;i<=m;i++){
			now=fz;
			for(int j=1;j<=n;j++){
				if(k[i][j]==1&&(fz&(1<<j-1)))
				now^=(1<<j-1);
				
				else if(k[i][j]==-1&&(!fz&(1<<j-1)))
				now|=(1<<j-1);
			}
			if(!f[now]){
				q.push( (zt_bs) {now,fb+1} );
				f[now]=1;
			}
		}
	}
	cout<<-true;
	return 0;
}