#include <bits/stdc++.h>
using namespace std;
#define rep2(i, m, n) for (int i = (m); i < (n); ++i)
#define rep(i, n) rep2(i, 0, n)
#define drep2(i, m, n) for (int i = (m)-1; i >= (n); --i)
#define drep(i, n) drep2(i, n, 0)
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#ifdef LOCAL
void debug_out() { cerr << endl; }
template <class Head, class... Tail> void debug_out(Head H, Tail... T) { cerr << ' ' << H; debug_out(T...); }
#define debug(...) cerr << 'L' << __LINE__ << " [" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#define dump(x) cerr << 'L' << __LINE__ << " " << #x << " = " << (x) << endl
#else
#define debug(...) (void(0))
#define dump(x) (void(0))
#endif
template<class T> using V = vector<T>;
using ll = long long;
using ld = long double;
using Vi = V<int>;  using VVi = V<Vi>;
using Vl = V<ll>;   using VVl = V<Vl>;
using Vd = V<ld>;   using VVd = V<Vd>;
using Vb = V<bool>; using VVb = V<Vb>;
template<class T> using priority_queue_rev = priority_queue<T, vector<T>, greater<T>>;
template<class T> vector<T> make_vec(size_t n, T a) { return vector<T>(n, a); }
template<class... Ts> auto make_vec(size_t n, Ts... ts) { return vector<decltype(make_vec(ts...))>(n, make_vec(ts...)); }
template<class T> inline int sz(const T &x) { return size(x); }
template<class T> inline bool chmin(T &a, const T b) { if (a > b) { a = b; return true; } return false; }
template<class T> inline bool chmax(T &a, const T b) { if (a < b) { a = b; return true; } return false; }
template<class T1, class T2> istream &operator>>(istream &is, pair<T1, T2> &p) { is >> p.first >> p.second; return is; }
template<class T1, class T2> ostream &operator<<(ostream &os, const pair<T1, T2> &p) { os << '(' << p.first << ", " << p.second << ')'; return os; }
template<class T, size_t n> istream &operator>>(istream &is, array<T, n> &v) { for (auto &e : v) is >> e; return is; }
template<class T, size_t n> ostream &operator<<(ostream &os, const  array<T, n> &v) { for (auto &e : v) os << e << ' '; return os; }
template<class T> istream &operator>>(istream &is, vector<T> &v) { for (auto &e : v) is >> e; return is; }
template<class T> ostream &operator<<(ostream &os, const vector<T> &v) { for (auto &e : v) os << e << ' '; return os; }
template<class T> inline void deduplicate(vector<T> &a) { sort(all(a)); a.erase(unique(all(a)), a.end()); }
template<class T> inline int count_between(const vector<T> &a, T l, T r) { return lower_bound(all(a), r) - lower_bound(all(a), l); } // [l, r)
inline ll cDiv(const ll x, const ll y) { return (x+y-1) / y; } // ceil(x/y)
inline int fLog2(const ll x) { assert(x > 0); return 63-__builtin_clzll(x); } // floor(log2(x))
inline int cLog2(const ll x) { assert(x > 0); return (x == 1) ? 0 : 64-__builtin_clzll(x-1); } // ceil(log2(x))
inline int popcount(const ll x) { return __builtin_popcountll(x); }
inline void fail() { cout << -1 << '\n'; exit(0); }
struct fast_ios { fast_ios(){ cin.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(20); }; } fast_ios_;
// const int INF  = (1<<30) - 1;
const ll INFll = (1ll<<60) - 1;
// const ld EPS   = 1e-10;
// const ld PI    = acos(-1.0);
// using mint = modint998244353;
// using mint = modint1000000007;
// using mint = modint;
// using Vm = V<mint>; using VVm = V<Vm>;


template<typename T>
struct edge {
  int v; T w;
  edge(int v, T w) : v(v), w(w) {}
};
template<typename T>
using Graph = vector<vector<edge<T>>>;

template<typename T>
vector<T> dijkstra(const Graph<T> &G, int s) {
  int n = G.size();
  const auto INF_T = numeric_limits<T>::max() / 2 - 1;
  vector<T> dist(n, INF_T);
  using PTi = pair<T, int>;
  priority_queue<PTi, vector<PTi>, function<bool(PTi, PTi)>> pq(
    [] (auto x, auto y) { return x.first > y.first; }
  );

  dist[s] = 0;
  pq.emplace(dist[s], s);
  
  while (!pq.empty()) {
    auto [d, u] = pq.top(); pq.pop();
    if (dist[u] < d) continue;
    for (auto &[v, w] : G[u]) if (chmin(dist[v], d + w)) pq.emplace(dist[v], v);
  }
  return dist;
}


int main() {
  int T, n, m; cin >> T >> n >> m;
  vector<array<ll, 3>> E(m); cin >> E;
  for (auto &[u, v, w] : E) --u, --v;

  ll ans = INFll;
  rep(i, m) {
    Graph<ll> G(n);
    int s, t, wst;
    rep(j, m) {
      auto [u, v, w] = E[j];
      if (j == i) s = v, t = u, wst = w;
      else {
        G[u].emplace_back(v, w);
        if (T == 0) G[v].emplace_back(u, w);
      }
    }
    auto dist = dijkstra(G, s);
    chmin(ans, dist[t] + wst);
  }

  if (ans == INFll) ans = -1;
  cout << ans << '\n';
}