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#include<bits/stdc++.h>
#define FOR(i,s,e) for(int i=(s);i<=(e);i++)
#define FORD(i,s,e) for(int i=(s);i>=(e);i--)
#define ALL(k) (k).begin(),(k).end()
#define e1 first 
#define e2 second
#define MP make_pair
#define PB push_back
#define EB emplace_back 
using namespace std;
typedef long long LL;
typedef pair<int,int> PII;
typedef pair<LL,LL> PLL;
typedef pair<int,PII> PIP;
typedef pair<PLL,PLL> PPP;
const int MAXN=211;
int odw[3][MAXN];
char aa[MAXN];
PII kraw[MAXN*MAXN];

main(){
	int n,b,r;scanf("%d%d%d",&n,&b,&r);
	int ilkr=0;
	FOR(i,1,n){
		scanf("%s",aa+1);
		FOR(j,1,n){
			if(aa[j]=='1'){
				ilkr++;
				kraw[ilkr]={i,j};
			}
		}
	}
	FOR(i,1,r){
		int a;scanf("%d",&a);
		odw[0][a]=1;
	}
	int i1=0,i2=1;
	int MAXW=((int)4e8)/(ilkr+n);
	FOR(kk,1,MAXW){
		swap(i1,i2);
		FOR(i,1,n) odw[i1][i]=0;
		FOR(i,1,ilkr){
			if(odw[i2][kraw[i].e1]) odw[i1][kraw[i].e2]=1;
		}
		int ok=1;
		FOR(i,b+1,n) if(odw[i1][i]) {ok=0;break;}
		if(ok==1) {printf("%d\n",kk);return 0;}
	}
	puts("-1");
}