#include <bits/stdc++.h>
//#include <chrono>
//#pragma GCC optimize("O3")
using namespace std;
#define reps(i,s,n) for(int i = s; i < n; i++)
#define rep(i,n) reps(i,0,n)
#define Rreps(i,n,e) for(int i = n - 1; i >= e; --i)
#define Rrep(i,n) Rreps(i,n,0)
#define ALL(a) a.begin(), a.end()

using ll = long long;
using vec = vector<ll>;
using mat = vector<vec>;

ll N,M,H,W,Q,K,A,B;
string S;
using P = pair<ll, ll>;
const ll INF = (1LL<<60);

template<class T> bool chmin(T &a, const T &b){
    if(a > b) {a = b; return true;}
    else return false;
}
template<class T> bool chmax(T &a, const T &b){
    if(a < b) {a = b; return true;}
    else return false;
}
template<class T> void my_printv(std::vector<T> v,bool endline = true){
    if(!v.empty()){
        for(std::size_t i{}; i<v.size()-1; ++i) std::cout<<v[i]<<" ";
        std::cout<<v.back();
    }
    if(endline) std::cout<<std::endl;
}

struct edge{
        int to, cost;
        edge(int a, int b) : to(a), cost(b){}
    };
using ve = vector<edge>;

int t;
ll solve(int pa, vector<ve> &G){
    vec dist(N, INF);
    vector<bool> used(N, false);
    dist[pa] = 0;
    priority_queue<P, vector<P>, greater<> > pque;
    pque.emplace(0, pa);
    ll res = INF;
    while(!pque.empty()){
        P p = pque.top(); pque.pop();
        int v = p.second;
        ll d = p.first;
        if(dist[v] < d) continue;
        used[v] = true;
        for(edge &e : G[v]){
            if(t == 0 && !used[e.to]) {
                if(d + e.cost + dist[e.to] == 6) cout<<v<<' '<<e.to<<endl;
                chmin(res, d + e.cost + dist[e.to]);
            }
            if(t == 1 && e.to == pa) chmin(res, d + e.cost);
            if(chmin(dist[e.to], d + e.cost)){
                pque.emplace(dist[e.to], e.to);
            }
        }
    }
    return res;
}

int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cin>>t;
    cin>>N>>M;
    vector<ve> G(N);
    rep(i, M){
        int u, v, w;
        cin>>u>>v>>w;
        --u; --v;
        G[u].emplace_back(v, w);
        if(t == 0) G[v].emplace_back(u, w);
    }
    ll res = INF;
    rep(i, N) chmin(res, solve(i, G));
    cout<<(res == INF ? -1 : res)<<endl;
}