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#include <iostream>
#include <algorithm>
#include <vector>
#include <string>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <cmath>
#include <cassert>
#include <cstring>
#include <ext/numeric>
#include <bitset>
using namespace std ;
using namespace __gnu_cxx ;
typedef long long LL ;
typedef pair<int,int> PII ;
typedef vector<int> VI ;
const int INF = 1e9+100 ;
const LL INFLL = (LL)INF * (LL)INF ;
#define REP(i,n) for(i=0;i<(n);++i)
#define ALL(c) c.begin(),c.end()
#define VAR(v,i) __typeof(i) v=(i)
#define FOREACH(i,c) for(VAR(i,(c).begin());i!=(c).end();++i)
#define CLEAR(t) memset(t,0,sizeof(t))
#define PB push_back
#define MP make_pair
#define FI first
#define SE second

template<class T1,class T2> ostream& operator<<(ostream &s, const pair<T1,T2> &x) { s<< "(" << x.FI << "," << x.SE << ")"; return s;}
template<class T>           ostream& operator<<(ostream &s, const vector<T>   &t) { FOREACH(it, t) s << *it << " " ; return s ; }
template<class T>           ostream& operator<<(ostream &s, const set<T>      &t) { FOREACH(it, t) s << *it << " " ; return s ; }
template<class T1,class T2> ostream& operator<<(ostream &s, const map<T1, T2> &t) { FOREACH(it, t) s << *it << " " ; return s ; }

///////////////////////////////////////////

const int MAXN = 200 ;
typedef bitset<MAXN> BITSET ;
BITSET G[MAXN] ;
BITSET goal ;

inline void ___try(const BITSET &x, int k) {
//	cout << k << ") " << x << endl ;
	if((x&goal)==x) {
		cout << k << endl ;
		exit(0) ;
	}
}
inline void step(const BITSET &a, int n, BITSET &ret) {
	ret.reset() ;
	int i ;
	REP(i,n)
		if(a[i]) ret |= G[i] ;
}

int main()
{
	ios_base::sync_with_stdio(0) ;
	int n, b, r, i, j, a ;
	char c ;
	cin >> n >> b >> r ;
	REP(i,n)
		REP(j,n) {
			cin >> c ;
			if(c=='1') G[i].set(j) ;
		}
	REP(i,b) goal.set(i) ;
	
	BITSET start ;
	while(r--) {
		cin >> a ;
		start.set(a-1) ;
	}
	
	___try(start, 0) ;
	
	BITSET p1=start, p2=start ;
	BITSET tmp ;
	for(int k=1 ; ; k++) {
		step(p2, n, tmp) ;
		___try(tmp, k) ;
		k++ ;
		step(tmp, n, p2) ;
		___try(p2, k) ;
		
		step(p1, n, tmp) ; p1 = tmp ;
		
		if(p2==p1) { // mamy cykl
			cout << -1 << endl ;
			return 0 ;
		}
	}
}