#include <bits/stdc++.h>
using namespace std;
const int MAXN = 210;
int n, m;
int d[MAXN][MAXN];
vector<pair<int, int> > e[MAXN];
vector<pair<double, double> > dis;
void init() {
  scanf("%d%d", &n, &m);
  memset(d, 0x3f, sizeof(d));
  for (int i = 1; i <= n; i++) d[i][i] = 0;
  for (int i = 1; i <= m; i++) {
    int u, v, w;
    scanf("%d%d%d", &u, &v, &w);
    d[u][v] = d[v][u] = min(d[u][v], w);
    e[u].push_back(make_pair(v, w));
    e[v].push_back(make_pair(u, w));
  }
}
void floyd() {
  for (int k = 1; k <= n; k++)
    for (int i = 1; i <= n; i++)
      for (int j = 1; j <= n; j++)
        if (d[i][k] + d[k][j] < d[i][j]) d[i][j] = d[i][k] + d[k][j];
}
bool check(int x) {
  double q = x / double(2.0);
  for (int i = 1; i <= n; i++) {
    for (int j = 0; j < e[i].size(); j++) {
      int a = i, b = e[i][j].first, L = e[i][j].second, k;
      dis.clear();
      for (k = 1; k <= n; k++) {
        double p1 = q - d[k][a];
        double p2 = q - d[k][b];
        if (p1 >= L) continue;
        if (p2 >= L) continue;
        if (p1 < 0 && p2 < 0) break;
        if (p1 + p2 >= L) continue;
        dis.push_back(make_pair(p1, L - p2));
      }
      if (k == n + 1) {
        if (dis.empty()) return true;
        double fuck = 0;
        sort(dis.begin(), dis.end());
        for (k = 0; k < dis.size(); k++) {
          if (fuck <= dis[k].first) return true;
          if (fuck < dis[k].second) fuck = dis[k].second;
        }
      }
    }
  }
  return false;
}
void solve() {
  int ll = 0, rr = 1000000000;
  int ans;
  while (ll <= rr) {
    int mid = (ll + rr) >> 1;
    if (check(mid)) {
      ans = mid;
      rr = mid - 1;
    } else
      ll = mid + 1;
  }
  printf("%.2lf\n", ans / double(2.0));
}
int main() {
  init();
  floyd();
  solve();
}
