#include <bits/stdc++.h>

using namespace std;

ifstream fin ("tunel.in");
ofstream fout ("tunel.out");

const double eps = 0.0000001;

vector<pair<int, int> >G[260];

int n, m;
double a[302][302], x[302];

int main()
{
  fin >> n >> m;
  for (int i = 1; i <= m; i++) {
    int x, y, c;
    fin >> x >> y >> c;
    G[x].push_back({y, c});
    G[y].push_back({x, c});
  }
  for (int i = 1; i < n; i++) {
    a[i][i] -= 1.0 * G[i].size();
    for (auto it : G[i]) {
      a[i][it.first] += 1.0;
      a[i][n + 1] -= 1.0 * it.second;
    }
  }
  for (int i = 1; i < n; i++)
    a[i][n] = 0.0;
  m = n; n--;
  int i = 1, j = 1;
  while (i <= n && j <= m) {
    int poz = -1;
    for (int k = i; k <= n; k++)
      if (abs(a[k][j]) > eps) {
        poz = k;
        break;
      }
    if (poz == -1) {
      j++;
      continue;
    }

    for (int k = 1; k <= m + 1; k++) {
      swap(a[i][k], a[poz][k]);
    }
    for(int k = j + 1; k <= m + 1; k++)
      a[i][k] = a[i][k] / a[i][j];
    a[i][j] = 1;
    for (int l1 = i + 1; l1 <= n; l1++) {
      for (int c1 = j +1; c1 <= m + 1; c1++)
        a[l1][c1] -= a[l1][j] * a[i][c1];
      a[l1][j] = 0;
    }
    i++;j++;
  }
  for(i = n; i > 0; i--)
    for(j = 1; j <= m; j++)
      if(abs(a[i][j]) > eps) {
        x[j] = a[i][m + 1];
        for(int k = j + 1; k <= m; k++)
          x[j] -= x[k] * a[i][k];
        break;
      }
  fout << x[1];
  return 0;
}