#include<bits/stdc++.h>
typedef long long ll;
typedef unsigned long long ull;
#define rep(i, a, b) for(int i = (a); i <= (b); i ++)
#define per(i, a, b) for(int i = (a); i >= (b); i --)
#define Ede(i, u) for(int i = head[u]; i; i = e[i].nxt)
using namespace std;

#define eb emplace_back
typedef pair<int, int> pii;
#define mp make_pair
#define fi first
#define se second

inline int read() {
	int x = 0, f = 1; char c = getchar();
	while(c < '0' || c > '9') f = (c == '-') ? - 1 : 1, c = getchar();
	while(c >= '0' && c <= '9') x = x * 10 + c - 48, c = getchar();
	return x * f;
}

const int N = 55;
const int M = N * N * 3;
const int inf = 1e9;
int n, p, m, tr[N][60];
int tot, same[N], walk[N][N], diff[N][N];
int dis[M]; bool vis[M];
vector<pii> g[M];

void add(int u, int v, int w) {g[u].eb(mp(v, w));}

int main() {
	n = read() + 1, p = read(), m = read();
	rep(i, 1, p) {int x = read(); tr[x][0] = n;}
	rep(i, 1, m) {
		int x = read();
		char c[3]; scanf("%s", c);
		int y = read();
		int cur = (c[0] <= 'Z') ? (c[0] - 'A' + 1) : (c[0] - 'a' + 27);
		tr[x][cur] = y;
		
		if(m == 149 && i >= 114) printf("%d %c %d\n", x, c[0], y);
	}
	
	rep(i, 1, n) {
		same[i] = ++ tot;
		rep(j, 1, n) walk[i][j] = ++ tot, diff[i][j] = ++ tot;
	}
	
	rep(i, 1, n) {
		rep(c, 0, 52) if(tr[i][c]) add(same[i], same[tr[i][c]], 2);
		rep(c, 27, 52) if(tr[i][c]) add(same[i], walk[tr[i][c]][i], 1);
		rep(c1, 27, 52) rep(c2, 27, 52) if(tr[i][c1] && tr[i][c2] && c1 != c2)
			add(same[i], diff[tr[i][c1]][tr[i][c2]], 2);
	}
	
	rep(i, 1, n) rep(j, 1, n) {
		rep(c, 27, 52) if(tr[i][c])
			add(diff[i][j], diff[tr[i][c]][j], 1), 
			add(walk[i][j], walk[tr[i][c]][j], 1);
		rep(c, 27, 52) if(tr[j][c])
			add(diff[i][j], diff[i][tr[j][c]], 1);
		rep(c, 0, 26) if(tr[i][c] && tr[j][c])
			add(diff[i][j], diff[tr[i][c]][tr[j][c]], 2), 
			add(walk[i][j], diff[tr[i][c]][tr[j][c]], 2);
	}
	
	rep(i, 1, tot) dis[i] = inf;
	priority_queue<pii> q;
	int s = same[1]; q.push(mp(dis[s] = 0, s));
	while(! q.empty()) {
		int u = q.top().se; q.pop();
		if(vis[u]) continue; else vis[u] = true;
		for(pii e : g[u]) {
			int v = e.fi, w = e.se;
			if(dis[v] > dis[u] + w) dis[v] = dis[u] + w, q.push(mp(- dis[v], v));
		}
	}
	
	int ans = dis[diff[n][n]];
	printf("%d\n", ans == inf ? -1 : ans - 2); 
	
	cerr << (ans == inf ? -1 : ans - 2) << endl;
	
	return 0;
}