#ifdef ONLINE_JUDGE
#pragma GCC target("avx2,avx")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#endif
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ull = unsigned long long;
using i128 = __int128_t;
using pii = pair<int, int>;
using pll = pair<long long, long long>;
template<class T> using vec = vector<T>;
template<class T> using vvec = vector<vector<T>>;
#define rep(i, n) for (int i = 0; i < (n); i++)
#define rrep(i, n) for (int i = int(n) - 1; i >= 0; i--)
#define all(x) (x).begin(), (x).end()
constexpr char ln = '\n';
istream& operator>>(istream& is, __int128_t& x) {
    x = 0;
    string s;
    is >> s;
    int n = int(s.size()), it = 0;
    if (s[0] == '-') it++;
    for (; it < n; it++) x = (x * 10 + s[it] - '0');
    if (s[0] == '-') x = -x;
    return is;
}
ostream& operator<<(ostream& os, __int128_t x) {
    if (x == 0) return os << 0;
    if (x < 0) os << '-', x = -x;
    deque<int> deq;
    while (x) deq.emplace_front(x % 10), x /= 10;
    for (int e : deq) os << e;
    return os;
}
template<class T1, class T2>
ostream& operator<<(ostream& os, const pair<T1, T2>& p) {
    return os << "(" << p.first << ", " << p.second << ")";
}
template<class T> 
ostream& operator<<(ostream& os, const vector<T>& v) {
    os << "{";
    for (int i = 0; i < int(v.size()); i++) {
        if (i) os << ", ";
        os << v[i];
    }
    return os << "}";
}
template<class Container> inline int SZ(Container& v) { return int(v.size()); }
template<class T> inline void UNIQUE(vector<T>& v) { v.erase(unique(v.begin(), v.end()), v.end()); }
template<class T1, class T2> inline bool chmax(T1& a, T2 b) { if (a < b) {a = b; return true ;} return false ;}
template<class T1, class T2> inline bool chmin(T1& a, T2 b) { if (a > b) {a = b; return true ;} return false ;}
inline int topbit(ull x) { return x == 0 ? -1 : 63 - __builtin_clzll(x); }
inline int botbit(ull x) { return x == 0 ? 64 : __builtin_ctzll(x); }
inline int popcount(ull x) { return __builtin_popcountll(x); }
inline int kthbit(ull x, int k) { return (x>>k) & 1; }
inline constexpr long long TEN(int x) { return x == 0 ? 1 : TEN(x-1) * 10; }
inline void print() { cout << "\n"; }
template<class T>
inline void print(const vector<T>& v) {
    for (int i = 0; i < int(v.size()); i++) {
        if (i) cout << " ";
        cout << v[i];
    }
    print();
}
template<class T, class... Args>
inline void print(const T& x, const Args& ... args) {
    cout << x << " ";
    print(args...);
}
#ifdef MINATO_LOCAL
inline void debug_out() { cerr << endl; }
template <class T, class... Args>
inline void debug_out(const T& x, const Args& ... args) {
    cerr << " " << x;
    debug_out(args...);
}
#define debug(...) cerr << __LINE__ << " : [" << #__VA_ARGS__ << "] =", debug_out(__VA_ARGS__)
#define dump(x) cerr << __LINE__ << " : " << #x << " = " << (x) << endl
#else
#define debug(...) (void(0))
#define dump(x) (void(0))
#endif
struct fast_ios { fast_ios() { cin.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(20); }; } fast_ios_;
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

template<typename T>
struct edge {
    int src,to;
    T cost;
    int id;

    edge(){}
    edge(int to, T cost) : src(-1), to(to), cost(cost), id(-1) {}
    edge(int src, int to, T cost) : src(src), to(to), cost(cost), id(-1) {}
    edge(int src, int to, T cost, int id) : src(src), to(to), cost(cost), id(id) {}
    bool operator<(const edge &e) const {return cost < e.cost;}
};

template<typename Int>
struct Dijkstra {
    struct Edge {
        int to;
        Int cost;
        Edge (int to, Int cost) : to(to), cost(cost) {}
        bool operator<(const Edge& o) const { return cost > o.cost; }
    };

    int n;
    Int INF;
    vector<vector<Edge>> g;
    vector<Int> dist;
    vector<int> from;

    Dijkstra() {}
    Dijkstra(int n, Int INF) : n(n), INF(INF), g(n), dist(n), from(n) {}

    void add_edge(int u, int v, Int cost) {
        assert(0 <= u and u < n);
        assert(0 <= v and v < n);
        g[u].emplace_back(v,cost);
    }

    void build(int s = 0) {
        fill(dist.begin(), dist.end(), INF);
        fill(from.begin(), from.end(), -1);
        dist[s] = 0;
        priority_queue<Edge> pq;
        pq.emplace(s, dist[s]);

        while (!pq.empty()) {
            Edge t = pq.top(); pq.pop();
            int v = t.to;
            Int d = t.cost;
            if (d > dist[v]) continue;
            for (Edge& e : g[v]) {
                if (dist[e.to] > d + e.cost) {
                    dist[e.to] = d + e.cost;
                    from[e.to] = v;
                    pq.emplace(e.to, dist[e.to]);
                }    
            }
        }
    }

    Int operator[](int k) { return dist[k]; }

    vector<int> restore(int to) {
        vector<int> ret;
        if (from[to] == -1) return ret;
        while (~to) {
            ret.emplace_back(to);
            to = from[to];
        }
        reverse(ret.begin(), ret.end());
        return ret;
    }
};

constexpr ll INF = 1e18;

int main() {
    int T; cin >> T;
    int N,M; cin >> N >> M;
    vec<edge<ll>> E(M);
    rep(i,M) {
        int u,v,w; cin >> u >> v >> w;
        u--; v--;
        E[i] = edge<ll>(u,v,w);
    }

    ll ans = INF;
    rep(x,M) {
        Dijkstra<ll> dist(N,INF);
        rep(i,M) {
            if (i==x) continue;
            dist.add_edge(E[i].src,E[i].to,E[i].cost);
            if (T==0) dist.add_edge(E[i].to,E[i].src,E[i].cost);
        }
        dist.build(E[x].to);
        chmin(ans,dist[E[x].src]+E[x].cost);
    }

    cout << (ans==INF ? -1 : ans) << ln;
}