#include <bits/stdc++.h>
using namespace std;
#define rep(i,a,n) for (int i=a;i<n;i++)
#define per(i,a,n) for (int i=n-1;i>=a;i--)
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define all(x) (x).begin(),(x).end()
#define fi first
#define se second
#define SZ(x) ((int)(x).size())
typedef vector<int> VI;
typedef basic_string<int> BI;
typedef long long ll;
typedef pair<int,int> PII;
typedef double db;
mt19937 mrand(random_device{}()); 
const ll mod=1000000007;
int rnd(int x) { return mrand() % x;}
ll powmod(ll a,ll b) {ll res=1;a%=mod; assert(b>=0); for(;b;b>>=1){if(b&1)res=res*a%mod;a=a*a%mod;}return res;}
ll gcd(ll a,ll b) { return b?gcd(b,a%b):a;}
// head

int n,p,t,go[55][55];
int same[55],go1[55][55],diff[55][55],tot;

const int N=101000;
typedef pair<int,int> PLI;
const int inf=1<<30;
vector<PII> e[N];
ll dis[N];
int vis[N];
priority_queue<PLI,vector<PLI>,greater<PLI>> hs;
void dijkstra(int S,int n) {
	rep(i,1,n+1) dis[i]=inf,vis[i]=0;
	dis[S]=0;
	hs.push(mp(dis[S],S));
	while (!hs.empty()) {
		int u=hs.top().se; hs.pop();
		if (vis[u]) continue;
		vis[u]=1;
		rep(j,0,SZ(e[u])) {
			int v=e[u][j].fi;
			if (dis[v]>dis[u]+e[u][j].se) {
				dis[v]=dis[u]+e[u][j].se;
				hs.push(mp(dis[v],v));
			}
		}
	}
}


void add(int u,int v,int w) {
	//printf("edge %d %d %d\n",u,v,w);
	e[u].pb(mp(v,w));
}
int main() {
	scanf("%d%d%d",&n,&p,&t);
	++n;
	rep(i,0,p) {
		int x;
		scanf("%d",&x);
		go[x][0]=n;
	}
	rep(i,0,t) {
		int u,v;
		char s[10];
		scanf("%d%s%d",&u,s,&v);
		if (s[0]<='Z') go[u][s[0]-'A'+1]=v;
		else go[u][s[0]-'a'+27]=v;
	}
	rep(i,1,n+1) same[i]=++tot;
	rep(i,1,n+1) rep(j,1,n+1) go1[i][j]=++tot;
	rep(i,1,n+1) rep(j,1,n+1) diff[i][j]=++tot;
	rep(i,1,n+1) {
		rep(c,0,53) if (go[i][c])
			add(same[i],same[go[i][c]],2);
		rep(c,27,53) if (go[i][c]) add(same[i],go1[go[i][c]][i],1);
		rep(c,27,53) rep(c2,27,53) if (c!=c2&&go[i][c]&&go[i][c2]) {
			add(same[i],diff[go[i][c]][go[i][c2]],2);
		}
	}
	rep(i,1,n+1) rep(j,1,n+1) {
		rep(c,27,53) {
			if (go[i][c]) {
				add(go1[i][j],go1[go[i][c]][j],1);
				add(diff[i][j],diff[go[i][c]][j],1);
			}
			if (go[j][c]) {
				add(diff[i][j],diff[i][go[j][c]],1);
			}
		}
		rep(c,0,27) if (go[i][c]&&go[j][c]) {
			add(go1[i][j],diff[go[i][c]][go[j][c]],2);
			add(diff[i][j],diff[go[i][c]][go[j][c]],2);
		}
	}
	dijkstra(same[1],tot);
	int ans=dis[diff[n][n]];
	if (ans==inf) ans=1;
	//printf("cnm %d %d %d\n",same[2],go1[3][2],go1[4][2]);
	printf("%d\n",ans-2);
}