#include <bits/stdc++.h>

using namespace std;

#define rng(i,a,b) for(int i=int(a);i<int(b);i++)
#define rep(i,b) rng(i,0,b)
#define repn(i,b) rng(i,1,b+1)
#define gnr(i,a,b) for(int i=int(b)-1;i>=int(a);i--)
#define per(i,b) gnr(i,0,b)
#define pb push_back
#define a first
#define b second
#define eb emplace_back
template<class t>using vc=vector<t>;
template<class t, class u>bool chmin(t &a, u b){
	if(a > b){ a = b; return true;}
	else return false;
}
const int inf = 100000000;
int n, p, m;
vc<int>A;
bool in[55];
vc<pair<int,char>>edge[55];
int dd[55][55];
#define mp make_pair
using P=pair<int,int>;
using Q=pair<int,pair<int,P>>;

int dist[55][55][27];
void slv(){
	cin>>n>>p>>m;
	rep(i,p){
		int v;cin>>v;
		A.pb(v);
		edge[v].eb(n+1, 'a');
	}
	in[n+1] = 1;
	rep(a,55)rep(b,55)if(a!=b)dd[a][b]=inf;
	rep(i,m){
		int u,v;string s;
		cin>>u>>s>>v;
		edge[u].eb(v, s[0]);
		chmin(dd[u][v],1);
	}
	repn(k,n)repn(i,n)repn(j,n)chmin(dd[i][j],dd[i][k]+dd[k][j]);
	auto iscap=[](char c){
		return 'A'<=c and c<='Z';
	};
	rep(a,55)rep(c,55)rep(d,27)dist[a][c][d]=inf;
	priority_queue<Q,vc<Q>,greater<Q>>que;
	
	repn(i,n){
		if(edge[i].size() < 2) continue;
		rep(j, edge[i].size()){
			rep(k, edge[i].size()){
				if(j==k)continue;
				char c = edge[i][j].b;
				int to = edge[i][j].a;
				char c2 = edge[i][k].b;
				int to2 = edge[i][k].a;
				
				if(iscap(c) == iscap(c2)){
					if(iscap(c) and c != c2) continue;
					
					if(chmin(dist[to][to2][26],dd[1][i]*2+2)) que.push(mp(dist[to][to2][26], mp(to,mp(to2,26))));
				}
				else if(iscap(c)){
					if(chmin(dist[to][to2][c-'A'],dd[1][i]*2+2)) que.push(mp(dist[to][to2][c-'A'], mp(to,mp(to2,c-'A'))));
				}
			}
		}
	}
	while(!que.empty()){
		auto qq = que.top(); que.pop();
		int cs = qq.a;
		int u = qq.b.a;
		int v = qq.b.b.a;
		int t = qq.b.b.b;
		//cout<<u<<" "<<v<<" "<<t<<" "<<cs<<endl;
		if(dist[u][v][t] != cs) continue;
		for(auto to:edge[v]){
			int nxt = to.a;
			char c = to.b;
			if(!iscap(c)){
				if(dist[u][nxt][t] > cs+1){
					dist[u][nxt][t] = cs+1;
					que.emplace(cs+1, mp(u,mp(nxt, t)));
				}
			}
			else {
				int uu, vv, tt;
				if(t == 26) {
					uu = nxt, vv = u, tt = c-'A';
				}
				else if(t == c-'A') uu=u,vv=nxt,tt=26;
				else continue;
				
				if(dist[uu][vv][tt] > cs+1){
					dist[uu][vv][tt] = cs+1;
					que.emplace(cs+1, mp(uu, mp(vv,tt)));
				}
			}
		}
		if(t == 26){
			for(auto to:edge[u]){
				int nxt = to.a;
				char c = to.b;
				if(!iscap(c)){
					if(dist[nxt][v][t] > cs+1){
						dist[nxt][v][t] = cs+1;
						que.emplace(cs+1, mp(nxt,mp(v, t)));
					}
				}
				else {
					int uu, vv, tt;
					{
						uu = nxt,vv = v, tt = c-'A';
					}
					if(dist[uu][vv][tt] > cs+1){
						dist[uu][vv][tt] = cs+1;
						que.emplace(cs+1, mp(uu, mp(vv,tt)));
					}
				}
			}
		}
	}
	int ans=dist[n+1][n+1][26]-2;
	if(ans > inf/2) ans = -1;
	cout<<ans<<endl;	
}	
signed main(){
	cin.tie(0);
	ios::sync_with_stdio(0);
	cout<<fixed<<setprecision(20);
	
	slv();
}