#include <cstdio>
#include <cstring>
#include <iostream>
#include <string>
#include <cmath>
#include <bitset>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <deque>
#include <algorithm>
#include <complex>
#include <unordered_map>
#include <unordered_set>
#include <random>
#include <cassert>
#include <fstream>
#include <utility>
#include <functional>
#include <stack>
#include <array>
#include <list>
#define popcount __builtin_popcount
using namespace std;
typedef long long int ll;
typedef pair<ll, int> P;

int main()
{
    int t; cin>>t;
    int n, m; cin>>n>>m;
    vector<P> g[2020];
    int u[2020], v[2020]; ll w[2020];
    for(int i=0; i<m; i++){
        cin>>u[i]>>v[i]>>w[i];u[i]--;v[i]--;
        g[u[i]].push_back({w[i], v[i]});
        if(t==0){
            g[v[i]].push_back({w[i], u[i]});
        }
    }
    ll d[2020];
    const ll INF=1e18;
    ll ans=INF;
    for(int k=0; k<m; k++){
        int i=v[k];
        for(int j=0; j<n; j++){
            d[j]=INF;
        }
        d[i]=0;
        priority_queue<P, vector<P>, greater<P>> que;
        que.push({0, i});
        while(!que.empty()){
            P p=que.top(); que.pop();
            int x=p.second;
            if(d[x]<p.first) continue;
            for(auto q:g[x]){
                int y=q.second;
                if(x==v[k] && y==u[k]) continue;
                if(d[y]>d[x]+q.first){
                    d[y]=d[x]+q.first;
                    que.push({d[y], y});
                }
            }
        }
        ans=min(ans, w[k]+d[u[k]]);
    }
    if(ans==INF) cout<<-1<<endl;
    else cout<<ans<<endl;
    return 0;
}