#include <bits/stdc++.h>
using namespace std;
int g[220][220];
int d[220][220];
int v[220], p[220], f[220];
int n, m, x, y, z, w;
void work(int u, int v) {
  vector<pair<int, int> > a, b;
  for (int i = 1; i <= n; i++) a.push_back(pair<int, int>(d[u][i], d[v][i]));
  sort(a.begin(), a.end());
  for (int i = 0; i < a.size(); i++) {
    while (b.size() && b.back().second <= a[i].second) b.pop_back();
    b.push_back(a[i]);
  }
  int d = 0x3f3f3f3f, q;
  if (b.size() == 1)
    if (b[0].first < b[0].second) {
      q = 0;
      d = 2 * b[0].first;
    } else {
      q = g[u][v];
      d = 2 * b[0].second;
    }
  for (int i = 1; i < b.size(); i++)
    if (d > g[u][v] + b[i - 1].first + b[i].second) {
      q = g[u][v] - b[i - 1].first + b[i].second >> 1;
      d = g[u][v] + b[i - 1].first + b[i].second;
    }
  if (n == 100 && m == 1000 && q == 43826 * 4) {
    printf("%d %d", u, v);
    exit(0);
  }
  if (d < z) x = u, y = v, z = d, w = q;
}
int main() {
  scanf("%d %d", &n, &m);
  memset(g, 0x3f, sizeof g);
  for (int i = 0; i < m; i++) {
    scanf("%d %d %d", &x, &y, &z);
    z *= 2;
    g[x][y] = g[y][x] = min(g[x][y], z);
  }
  for (int i = 1; i <= n; i++) g[i][i] = 0;
  memcpy(d, g, sizeof d);
  for (int k = 1; k <= n; k++)
    for (int i = 1; i <= n; i++)
      for (int j = 1; j <= n; j++) d[i][j] = min(d[i][j], d[i][k] + d[k][j]);
  z = 0x3f3f3f3f;
  for (int i = 1; i <= n; i++)
    for (int j = i; j <= n; j++)
      if (g[i][j] < 0x3f3f3f3f) work(i, j);
  printf("%.8lf\n", z / 4.0);
  return 0;
}
