#include <fstream>
#include <vector>
#include <iomanip>

using namespace std;

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

const int max_size = 260;
const double eps = 1e-3;

vector <pair <int, int>> mc[max_size];
double sis[max_size][max_size];

int main ()
{
    int n, m;
    in >> n >> m;
    while (m--)
    {
        int x, y, c;
        in >> x >> y >> c;
        mc[x].push_back({y, c});
        mc[y].push_back({x, c});
    }
    for (int i = 1; i < n; i++)
    {
        sis[i][i] = mc[i].size();
        for (auto f : mc[i])
        {
            sis[i][f.first]--; // coaie
            sis[i][n + 1] += f.second;
        }
    }
    sis[n][n] = 1;
    int i = 1;
    while (i <= n)
    {
        int k;
        for (k = i; k <= n; k++)
        {
            if (sis[k][i] <= -eps || sis[k][i] >= eps)
            {
                break;
            }
        }
        for (int p = 1; p <= n + 1; p++)
        {
            swap(sis[i][p], sis[k][p]);
        }
        for (int p = i + 1; p <= n + 1; p++)
        {
            sis[i][p] /= sis[i][i];
        }
        sis[i][i] = 1;
        for (int p = 1; p <= n; p++)
        {
            if (p == i)
            {
                continue;
            }
            for (int q = 1; q <= n + 1; q++)
            {
                if (q == i)
                {
                    continue;
                }
                sis[p][q] -= sis[p][i] * sis[i][q];
            }
            sis[p][i] = 0;
        }
        i++;
    }
    for (int i = 1; i <= n; i++)
    {
        for (int j = 1; j <= n + 1; j ++)
        {
            //out << sis[i][j] << " ";
        }
        //out << '\n';
    }
    out << fixed << setprecision(4) << sis[1][n + 1];
    in.close();
    out.close();
    return 0;
}