#include<bits/stdc++.h>
using namespace std;
inline int read()
{
    int x=0,w=1;
    char ch=0;
    while(ch<'0'||ch>'9')
    {
        if(ch=='-') w=-1;
        ch=getchar();
    }
    while(ch>='0'&&ch<='9')
    {
        x=(x<<1)+(x<<3)+(ch^48);
        ch=getchar();
    }
    return x*w;
}
inline void write(int x) 
{
    if(x<0) 
    { 
        x=-x;
        putchar('-');
    }
    if(x>=10) write(x/10);
    putchar((x%10)^48);
}
const int N=5e4+5,K=55;
bool s[K][K],vis[N];
int b[N],n,k,dis[N];
void dijkstra(int ss)
{
    memset(dis,0x3f,sizeof(dis));
    priority_queue<pair<int,int>,vector<pair<int,int>>,greater<pair<int,int>>> q;
    dis[ss]=0;
    q.push({0,ss});
    while(!q.empty())
    {
        int u=q.top().second;
        q.pop();
        if(vis[u]) continue;
        vis[u]=1;
        for(int i=1;i<=n;i++)
        {
            if(!vis[i]&&dis[i]>dis[u]+abs(i-u)&&s[b[u]][b[i]])
            {
                dis[i]=dis[u]+abs(i-u);
                q.push({dis[i],i});
            }
        }
    }
}
int main()
{
    freopen("telephone.in","r",stdin);
    freopen("telephone.out","w",stdout);
    n=read(),k=read();
    for(int i=1;i<=n;i++) b[i]=read();
    for(int i=1;i<=k;i++)
    {
        string str;
        cin>>str;
        for(int j=0;j<k;j++) s[i][j+1]=str[j]^48;
    }
    dijkstra(1);
    if(dis[n]!=0x3f3f3f3f) write(dis[n]);
    else write(-1);
    fclose(stdin);
    fclose(stdout);
	return 0;
}