#include <bits/stdc++.h>

typedef long long LL;

const int N = 2e3 + 7;
const LL INF = 0x3f3f3f3f3f3f3f3f;

int n, m, pre[N];
LL dis[N];
std::vector<std::pair<int, int>> g[N];

void dijkstra(int r) {
  std::priority_queue<std::pair<LL, int>, std::vector<std::pair<LL, int>>, std::greater<>> q;
  memset(pre, 0, sizeof pre);
  memset(dis, 0x3f, sizeof dis);
  dis[r] = 0, q.push({0, r});
  while(!q.empty()) {
    auto [d, u] = q.top();
    q.pop();
    if(d != dis[u])
      continue;
    for(auto &&[v, w]: g[u])
      if(dis[v] > d + w) {
	dis[v] = d + w;
	pre[v] = u;
	q.push({dis[v], v});
      }
  }
}

void undir() {
  scanf("%d%d", &n, &m);
  for(int i = 1, x, y, z; i <= m; ++i) {
    scanf("%d%d%d", &x, &y, &z);
    g[x].emplace_back(y, z);
    g[y].emplace_back(x, z);
  }
  LL ans = INF;
  for(int r = 1; r <= n; ++r) {
    dijkstra(r);
    for(int u = 1; u <= n; ++u)
      for(auto &&[v, w]: g[u])
	if(pre[u] != v && pre[v] != u)
	  ans = std::min(ans, dis[u] + dis[v] + w);
  }
  printf("%lld\n", ans == INF ? -1 : ans);
}

void dir() {
  scanf("%d%d", &n, &m);
  for(int i = 1, x, y, z; i <= m; ++i) {
    scanf("%d%d%d", &x, &y, &z);
    g[x].emplace_back(y, z);
  }
  LL ans = INF;
  for(int r = 1; r <= n; ++r) {
    dijkstra(r);
    for(int u = 1; u <= n; ++u)
      for(auto &&[v, w]: g[u])
	if(v == r)
	  ans = std::min(ans, dis[u] + w);
  }
  printf("%lld\n", ans == INF ? -1 : ans);
}	

int main() {

  int cas;
  scanf("%d", &cas);

  if(cas == 0)
    undir();
  else
    dir();

  return 0;

}