#include <string>
#include <iostream>
#include <vector>
#include <queue>

using namespace std;
int T, N, M;
int U[2000], V[2000];
long long W[2000];

long long dijkstra(int src, int dst, int id) {
    vector<vector<pair<int, long long>>> G(N);
    for (int i = 0; i < M; ++i) if (i != id) {
        G[U[i]].push_back(make_pair(V[i], W[i]));
        if (T == 0) {
            G[V[i]].push_back(make_pair(U[i], W[i]));
        }
    }
    vector<long long> d(N, (long long)1e18);
    priority_queue<pair<long long, int>> pq;
    pq.push(make_pair(0, src));
    d[src] = 0;
    while (!pq.empty()) {
        auto p = pq.top();
        auto cost = -p.first;
        auto u = p.second;
        pq.pop();
        if (d[u] < cost) continue;
        for (auto e:G[u]) {
            int v = e.first;
            long long nd = d[u] + e.second;
            if (d[v] > nd) {
                d[v] = nd;
                pq.push(make_pair(-nd, v));
            }
        }
    }
    return d[dst];
}

main() {
    cin >> T >> N >> M;
    for (int i = 0; i < M; ++i) {
        cin >> U[i] >> V[i] >> W[i];
        --U[i];--V[i];
    }
    long long INF = 1e18;
    long long ans = INF;
    for (int i = 0; i < M; ++i) {
        ans = min(ans, dijkstra(V[i], U[i], i) + W[i]);
    }
    cout << (ans == INF ? -1 : ans )<< endl;
}