#include <bits/stdc++.h>
using namespace std;
const int maxn = 222;
int dp[maxn][maxn];
const int maxx = 1e9 + 7;
int n, m;
struct edge {
  int u, v, w;
};
edge e[maxn * maxn];
struct node {
  int a, b;
} p[maxn];
bool cmp1(const node &a, const node &b) { return a.a > b.a; }
int main() {
  scanf("%d %d", &n, &m);
  for (int i = 1; i <= n; i++) {
    for (int j = 1; j <= n; j++)
      if (i != j) dp[i][j] = maxx;
  }
  for (int i = 0; i < m; i++) {
    scanf("%d %d %d", &e[i].u, &e[i].v, &e[i].w);
    dp[e[i].u][e[i].v] = dp[e[i].v][e[i].u] = e[i].w;
  }
  for (int k = 1; k <= n; k++) {
    for (int j = 1; j <= n; j++) {
      for (int i = 1; i <= n; i++) {
        dp[j][i] = min(dp[j][i], dp[j][k] + dp[k][i]);
      }
    }
  }
  int cmp;
  int ans = maxx;
  for (int i = 0; i < m; i++) {
    int sb = 0;
    int u = e[i].u;
    int v = e[i].v;
    int c = e[i].w;
    for (int j = 1; j <= n; j++) {
      p[j].a = dp[u][j];
      p[j].b = dp[v][j];
    }
    sort(p + 1, p + 1 + n, cmp1);
    for (int j = 1; j <= n; j++) {
      if (abs(p[j].a - sb) <= c)
        cmp = p[j].a + sb + c;
      else
        cmp = max(sb, p[j].a) * 2;
      ans = min(cmp, ans);
      sb = max(p[j].b, sb);
    }
  }
  if (ans % 2)
    printf("%d.5\n", ans / 2);
  else
    printf("%d\n", ans / 2);
  return 0;
}
