#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using pl = pair<ll,ll>;
using pii = pair<int,int>;
using tpl = tuple<int,int,int>;
#define all(a) a.begin(), a.end()
#define filter(a) a.erase(unique(all(a)), a.end())
const int mn = 1e5 + 5;
const int maxStage = 4;
struct candidates : vector<pii> {
bool push (int cand, int source) {
int inserted = -1;
for (int i = 0; i < size(); i++) {
int cur, s; tie(cur, s) = (*this)[i];
if (cand < cur) {
inserted = i;
insert((*this).begin() + i, make_pair(cand, source));
break;
}
else if (s == source) return 0;
}
if (inserted != -1) {
for (int i = inserted + 1; i < size(); i++)
if ((*this)[i].second == source)
return erase((*this).begin() + i), 1;
if (size() > maxStage) return pop_back(), 1;
}
else {
if (size() < maxStage) return emplace_back(cand, source), 1;
else return 0;
}
}
} dist[mn];
struct IT {
vector<int> tr;
IT (int sz) : tr(4 * sz, INT_MAX) {}
void update (int pos, int val, int k, int l, int r) {
for (; l < r;) {
int mid = (l + r) >> 1;
if (pos <= mid) k <<= 1, r = mid;
else k <<= 1, k |= 1, l = mid + 1;
}
tr[k] = min(tr[k], val);
for (k >>= 1; k; k >>= 1)
tr[k]= min(tr[k << 1], tr[k << 1 | 1]);
}
int query (int a, int b, int k, int l, int r) {
if (b < l || r < a) return INT_MAX;
if (a <= l && r <= b) return tr[k];
int mid = (l + r) >> 1;
return min(query(a, b, k << 1, l, mid), query(a, b, k << 1 | 1, mid + 1, r));
}
};
priority_queue<tpl, vector<tpl>, greater<tpl>> pq;
vector<pii> adj[mn], path[mn];
vector<int> visSource[mn];
int visTime[mn], spec[mn], n, m, k;
bool check (int u, int targ) {
return find(all(visSource[u]), targ) != visSource[u].end();
}
int main()
{
ios::sync_with_stdio(0);
cin.tie(0);
/// read input & preprocess
cin >> n >> m >> k;
while (m--) {
int a, b, c; cin >> a >> b >> c;
adj[a].emplace_back(b, c);
adj[b].emplace_back(a, c);
}
for (int i = 1; i <= k; i++) {
cin >> spec[i];
pq.emplace(0, spec[i], spec[i]);
dist[spec[i]].emplace_back(0, spec[i]);
}
/// multi-core dijkstra
int threshold = 0;
while (pq.size() && threshold < 5 * n) {
int dst, u, source; tie(dst, u, source) = pq.top(); pq.pop();
if (visTime[u] == maxStage || check(u, source)) continue;
visTime[u]++, threshold++;
for (pii item : adj[u]) {
int v, w; tie(v, w) = item;
if (dist[v].push(dst + w, source))
pq.emplace(dst + w, v, source);
}
}
/// combine 2 paths
for (int i = 1; i <= k; i++) {
int u = spec[i];
for (auto [dist, source] : dist[u])
if (u != source) path[min(source, u)].emplace_back(max(source, u), dist);
}
IT tree(n); int ans = INT_MAX;
for (int i = 1; i <= n; i++) {
for (auto [v, weight] : path[i]) {
int cur = min({tree.query(1, i - 1, 1, 1, n),
tree.query(i + 1, v - 1, 1, 1, n),
tree.query(v + 1, n, 1, 1, n)});
if (cur != INT_MAX) ans = min(ans, weight + cur);
}
for (auto [v, weight] : path[i])
tree.update(v, weight, 1, 1, n);
}
cout << (ans == INT_MAX ? -1 : ans);
return 0;
}
