#include <queue>
#include <vector>
#include <iostream>
using namespace std;
int main() {
    int t, n, m; cin >> t >> n >> m;
    vector<pair<int, int> > adj[n];
    int weight[m];
    for (int i = 0; i < m; i++) {
        int u, v, w; cin >> u >> v >> w;
        u--; v--;
        adj[u].emplace_back(v, i);
        if (t == 0) adj[v].emplace_back(u, i);
        weight[i] = w;
    }
    long long ans = 1LL<<60;
    for (int u = 0; u < n; u++)
        for (auto [v, i] : adj[u]) {
            vector<long long> dist(n, 1LL<<60);
            priority_queue<pair<long long, int> > pq;
            dist[v] = 0;
            pq.push({0, v});
            while (!pq.empty()) {
                long long d = -pq.top().first;
                int x = pq.top().second;
                pq.pop();
                if (d > dist[x]) continue;
                for (auto [y, j] : adj[x]) {
                    if (j == i) continue;
                    if (dist[y] <= dist[x] + weight[j]) continue;
                    dist[y] = dist[x] + weight[j];
                    pq.push({-dist[y], y});
                }
            }
            ans = min(ans, dist[u] + weight[i]);
        }
    cout << (ans < 1LL<<60 ? ans : -1) << endl;
}