#include <bits/stdc++.h>
using namespace std;
inline void read(int &x) {
  int v = 0, f = 1;
  char c = getchar();
  while (!isdigit(c) && c != '-') c = getchar();
  if (c == '-')
    f = -1;
  else
    v = v * 10 + c - '0';
  while (isdigit(c = getchar())) v = v * 10 + c - '0';
  x = v * f;
}
inline void read(long long &x) {
  long long v = 0ll, f = 1ll;
  char c = getchar();
  while (!isdigit(c) && c != '-') c = getchar();
  if (c == '-')
    f = -1;
  else
    v = v * 10 + c - '0';
  while (isdigit(c = getchar())) v = v * 10 + c - '0';
  x = v * f;
}
inline void readc(char &x) {
  char c;
  while ((c = getchar()) == ' ')
    ;
  x = c;
}
inline void writes(string s) { puts(s.c_str()); }
inline void writeln() { writes(""); }
inline void writei(int x) {
  if (x < 0) {
    putchar('-');
    x = abs(x);
  }
  if (!x) putchar('0');
  char a[25];
  int top = 0;
  while (x) {
    a[++top] = (x % 10) + '0';
    x /= 10;
  }
  while (top) {
    putchar(a[top]);
    top--;
  }
}
inline void writell(long long x) {
  if (x < 0) {
    putchar('-');
    x = abs(x);
  }
  if (!x) putchar('0');
  char a[25];
  int top = 0;
  while (x) {
    a[++top] = (x % 10) + '0';
    x /= 10;
  }
  while (top) {
    putchar(a[top]);
    top--;
  }
}
int n, m, i, j, k, px[40005], py[40005], l, r, mid, ans, rk[205][205],
    pz[40005], dis[205][205];
bool cmp(int x, int y) { return dis[i][x] < dis[i][y]; }
int main() {
  scanf("%d%d", &n, &m);
  for (((i)) = (1); ((i)) <= ((n)); ((i))++)
    for (((j)) = (1); ((j)) <= ((n)); ((j))++)
      dis[i][j] = (i == j ? 0 : 0x3bbbbbbb);
  for (((i)) = (1); ((i)) <= ((m)); ((i))++) {
    scanf("%d%d%d", &px[i], &py[i], &pz[i]);
    dis[px[i]][py[i]] = dis[py[i]][px[i]] = pz[i];
  }
  for (((k)) = (1); ((k)) <= ((n)); ((k))++) {
    for (((i)) = (1); ((i)) <= ((n)); ((i))++) {
      for (((j)) = (1); ((j)) <= ((n)); ((j))++) {
        dis[i][j] = min(dis[i][k] + dis[k][j], dis[i][j]);
      }
    }
  }
  ans = 0x3bbbbbbb;
  for (((i)) = (1); ((i)) <= ((n)); ((i))++) {
    int lys = 0;
    for (((j)) = (1); ((j)) <= ((n)); ((j))++) {
      lys = max(lys, dis[i][j]);
      rk[i][j] = j;
    }
    ans = min(ans, lys + lys);
    stable_sort(rk[i] + 1, rk[i] + n + 1, cmp);
  }
  for (((i)) = (1); ((i)) <= ((m)); ((i))++) {
    int lst = 0;
    for (((j)) = ((n)); ((j)) >= (1); ((j))--) {
      int id = rk[px[i]][j];
      if (!lst) {
        lst = id;
        continue;
      }
      if (dis[py[i]][id] > dis[py[i]][lst]) {
        ans = min(ans, dis[px[i]][id] + dis[py[i]][lst] + pz[i]);
        lst = id;
      }
    }
  }
  printf("%.10f\n", ans / 2.0);
  return 0;
}
