#include<bits/stdc++.h>
using namespace std;
const int N=1e5+10,K=55,INF=0x3f3f3f3f;
typedef pair<int,int> PII;
int n,k;
int b[N],dis[N];
bool a[K][K];
vector<int> pos[K];
int dijkstra(){
	memset(dis,0x3f,sizeof(dis));dis[1]=0;
	priority_queue<PII,vector<PII>,greater<PII> > pq;
	pq.push(make_pair(0,1));
	while(!pq.empty()){
		int d=pq.top().first,u=pq.top().second;
		pq.pop();
		if (u==n){
			return d;
		}
		if (d>dis[u]) continue;
		for(int i=1;i<=k;i++){
			if(a[b[u]][i]){
				for(int j=0;j<(int)pos[i].size();j++){
					int x=pos[i][j];
					if(dis[x]>dis[u]+abs(u-x)){
						dis[x]=dis[u]+abs(u-x);
						pq.push(make_pair(dis[x],x));
					}
				}
			}
		}
	}
	return dis[n];
}
int main() {
	freopen("telephone.in", "r", stdin);
	freopen("telephone.out", "w", stdout);
	ios::sync_with_stdio(false);
	cin.tie(0);
	cin>>n>>k;
	for(int i=1;i<=n;i++){
		cin>>b[i];
		pos[b[i]].push_back(i);
	}
	for (int i=1;i<=k;i++) {
		string s;
		cin>>s;
		for (int j=1;j<=k;j++) {
			if(s[j-1]=='0'){
				a[i][j]=0;
			}else{
				a[i][j]=1;
			}
		}
	}
	int f=dijkstra();
	if(f==0x3f3f3f3f){
		cout<<-1<<endl;
	}else{
		cout<<f<<endl;
	}
	return 0;
}