#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
using P = pair<ll, int>;
const ll INF = 10000000000000;

int main() {
	cin.tie(nullptr); ios_base::sync_with_stdio(false);
	int t; cin >> t;
	int n, m; cin >> n >> m;
	vector<vector<P>> adj(n);
	for (int z = 0; z < m; ++z) {
		int u, v; ll w; cin >> u >> v >> w;
		u--; v--;
		adj[u].push_back(P(w, v));
		if (t == 0) adj[v].push_back(P(w, u));
	}
	
	ll ans = INF;
	for (int x = 0; x < n; ++x) {
		vector<ll> dist(n, INF);
		vector<int> prev(n, -1);
		dist[x] = 0;
		priority_queue<P, vector<P>, greater<P>> q;
		q.push(P(0ll, x));
		while (!q.empty()) {
			P z = q.top(); q.pop();
			ll c0 = z.first; int i = z.second;
			for (P y : adj[i]) {
				ll c1 = y.first; int j = y.second;
				if (t == 0 and prev[i] == j) continue;
				if (dist[j] > c0 + c1) {
					prev[j] = i;
					dist[j] = c0 + c1;
					q.push(P(c0 + c1, j));
				}
				else if (t == 0 or j == x) {
					ans = min(ans, c0 + dist[j] + c1);
				}
			}
		}
	}
	cout << (ans < INF ? ans : -1) << endl;
	return 0;
}