#include<bits/stdc++.h>

using namespace std;
using pl=pair<long long,long long>;
using Graph=vector<vector<long long>>;

long long shortest_cycle(long long n,long long m,vector<long long> &u,vector<long long> &v,vector<long long> &w,bool isdirected){
  long long res=8e18;
  Graph g(n);
  vector<pl> vp;
  for(int i=0;i<m;i++){
    g[u[i]].push_back(i);
    if(!isdirected){
      g[v[i]].push_back(i);
    }
    vp.push_back({w[i],i});
  }
  sort(vp.begin(),vp.end());

  for(int ec=0;ec<m;ec++){
    long long eid=vp[ec].second;
    if(w[eid]>=res){break;}
    priority_queue<pl,vector<pl>,greater<pl>> pq;
    pq.push({w[eid],v[eid]});
    vector<long long> d(n,8e18);
    d[v[eid]]=w[eid];
    while(!pq.empty()){
      pl od=pq.top();pq.pop();
      if(od.first>=res){break;}
      if(od.second==u[eid]){res=min(res,od.first);break;}
      for(auto &nx : g[od.second]){
        if(nx==eid){continue;}
        long long nv=(u[nx]^v[nx]^od.second);
        long long nd=od.first+w[nx];
        if(d[nv]>nd){
          d[nv]=nd;
          pq.push({nd,nv});
        }
      }
    }
  }
  if(res>7e18){res=-1;}
  return res;
}

int main(){
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  int t;
  cin >> t;
  bool isdirected;
  if(t==0){isdirected=false;}
  else{isdirected=true;}
  long long n,m;
  cin >> n >> m;
  vector<long long> u(m),v(m),w(m);
  for(int i=0;i<m;i++){
    cin >> u[i] >> v[i] >> w[i];
    u[i]--;v[i]--;
  }
  cout << shortest_cycle(n,m,u,v,w,isdirected) << '\n';
  return 0;
}