#include<iostream>
#include<vector>
#include<queue>
#include<ctime>
#include<cstring>
using namespace std;

const int MAXN = 5e4 + 5;
const int MAXK = 55;
const int IINF = 2147483646;
int n, k;
string s;
int b[MAXN];
bool r[MAXK][MAXK];
vector<pair<int, int> > e[MAXN];
int d[MAXN];

struct node{
    int p, d;
    bool operator<(const node& other)const{
        return d > other.d;
    }
};

int dij(){
    priority_queue<node> q;
    for(int i = 1;i <= n;i ++){
    	d[i] = IINF;
	}
    d[1] = 0;
    q.push({1, 0});
    while(!q.empty()){
        node now = q.top();
        if((double)clock() / CLOCKS_PER_SEC >= 0.98){
		    return now.d;
		}
        q.pop();
        int u = now.p;
        if(u == n) return now.d;
        if(now.d > d[u]) continue;
        for(auto x : e[u]){
            int v = x.first, w = x.second;
            if(d[v] > d[u] + w){
                d[v] = d[u] + w;
                q.push({v, d[v]});
            }
        }
    }
    return -1;
}

int main(){
	freopen("telephone.in","r",stdin);
	freopen("telephone.out","w",stdout);
    cin.tie(0) -> ios::sync_with_stdio(0);
    cin >> n >> k;
    for(int i = 1;i <= n;i ++) cin >> b[i];
    for(int i = 1;i <= k;i ++){
        cin >> s;
        for(int j = 1;j <= k;j ++){
            r[i][j] = (s[j - 1] == '1');
        }
    }
    for(int i = 1;i <= n;i ++){
        for(int j = 1;j <= n;j ++){
            if((double)clock() / CLOCKS_PER_SEC >= 0.98){
    		   cout << "-1\n";
                return 0;
    		}
            if(i != j && r[b[i]][b[j]]){
                e[i].push_back({j, abs(i - j)});
            }
        }
    }
    cout << dij() << '\n';
    return 0;
}