#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <queue>
#include <string>
#include <map>
#include <set>
#include <stack>
#include <tuple>
#include <deque>
#include <array>
#include <numeric>
#include <bitset>
#include <iomanip>
#include <cassert>
#include <chrono>
#include <random>
#include <limits>
#include <iterator>
#include <functional>
#include <sstream>
#include <fstream>
#include <complex>
#include <cstring>
#include <unordered_map>
#include <unordered_set>
using namespace std;

using ll = long long;
using P = pair<int, int>;
constexpr int INF = 1001001001;
constexpr int mod = 1000000007;
// constexpr int mod = 998244353;

template<class T>
inline bool chmax(T& x, T y){
    if(x < y){
        x = y;
        return true;
    }
    return false;
}
template<class T>
inline bool chmin(T& x, T y){
    if(x > y){
        x = y;
        return true;
    }
    return false;
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int T, N, M;
    cin >> T >> N >> M;
    using edge = tuple<int, int, int>;
    vector<vector<edge>> graph(N);
    vector<int> u(M), v(M), w(M);
    for(int i = 0; i < M; ++i){
        cin >> u[i] >> v[i] >> w[i];
        --u[i], --v[i];
        graph[u[i]].emplace_back(v[i], w[i], i);
        if(T == 0)  graph[v[i]].emplace_back(u[i], w[i], i);
    }

    constexpr ll inf = 1e+17;
    ll ans = inf;
    for(int ban = 0; ban < M; ++ban){
        vector<ll> dist(N, inf);
        dist[v[ban]] = 0;
        using Data = pair<ll, int>;
        priority_queue<Data, vector<Data>, greater<Data>> que;
        que.emplace(0, v[ban]);
        while(!que.empty()){
            auto [d, from] = que.top();
            que.pop();
            if(d > dist[from])  continue;
            for(auto [to, cost, id] : graph[from]){
                if(id != ban && chmin(dist[to], dist[from] + cost)){
                    que.emplace(dist[to], to);
                }
            }
        }
        chmin(ans, dist[u[ban]] + w[ban]);
    }

    if(ans == inf)  ans = -1;
    cout << ans << endl;

    return 0;
}