#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <queue>
#include <cstring>
#include <cstdlib>
#include <cmath>
using namespace std;
using ll = long long;

struct Graph {
    static constexpr ll INF = 1LL << 60;
    struct VertexQ {
        bool operator<(const VertexQ &o) const {
            return c > o.c; // 逆
        }
        int i;
        ll c;
    };
    struct Vertex { int n; ll c; };
    struct Edge { int i, n, c; };
    Graph(int n, int m) : v(n, { -1, INF }), e(m), n(n), m(0) {}
    void add_edge(int a, int b, int c) {
        e[m] = { b, v[a].n, c };
        v[a].n = m;
        m++;
    }
    void dijkstra(int i, int i1) {
        for (int i = 0; i < n; i++) v[i].c = INF;
        priority_queue<VertexQ> q;
        q.push({ i, v[i].c = 0 });
        while (!q.empty()) {
            auto p = q.top(); q.pop();
            if (p.i == i1) break;
            if (p.c > v[p.i].c) continue;
            for (int j = v[p.i].n; j >= 0; j = e[j].n) {
                Edge &o = e[j];
                if (p.i == i && o.i == i1) continue;
                ll c = p.c + o.c;
                if (c < v[o.i].c) q.push({ o.i, v[o.i].c = c });
            }
        }
    }
    void solve() {
        ll r = INF;
        for (int i = 0; i < n; i++) {
            for (int j = v[i].n; j >= 0; j = e[j].n) {
                Edge &o = e[j];
                dijkstra(o.i, i);
                r = min(r, v[i].c + o.c);
            }
        }
        if (r == INF) r = -1;
        cout << r << endl;
    }
    vector<Vertex> v;
    vector<Edge> e;
    int n, m;
};

int main() {
    int t;
    cin >> t;

    int n, m;
    cin >> n >> m;

    Graph g(n, m * (t == 0 ? 2 : 1));
    for (int i = 0; i < m; i++) {
        int u, v, w;
        cin >> u >> v >> w;
        u--; v--;

        g.add_edge(u, v, w);
        if (t == 0) g.add_edge(v, u, w);
    }

    g.solve();

    return 0;
}