#include<stdio.h>
#include<vector>

FILE *re, *we;

using namespace std;

const int MAXN = 256;
int n, m;


struct val
{
    int no, co;
};

vector <val> g[MAXN];

double mg[MAXN][MAXN];
bool viz[MAXN];

void sterge(int de, int ce, int poz)
{
    double c = mg[ce][poz];
    double d = mg[de][poz];

    for(int i = 0; i < n; i++) {
        mg[de][i] -= ((mg[ce][i] * d) / c);
    }
}

int main ()
{
    we = fopen("tunel.out", "w");
    re = fopen("tunel.in", "r");
    fscanf(re, "%d%d", &n, &m);

    for(int i = 0; i < m; i++) {
        int a, b, c;

        fscanf(re, "%d%d%d", &a, &b, &c);
        val nou;
        nou.no = b;
        nou.co = c;
        g[a].push_back(nou);
        nou.no = a;
        g[b].push_back(nou);
    }

    for(int i = 1; i < n; i++) {
        for(auto &it : g[i]) {
            mg[i][0] += it.co;
            mg[i][it.no] = -1;
        }
        mg[i][i] = (g[i].size());
        mg[i][n] = 0;
    }

    for(int i = 1; i < n; i++) {
        for(int j = 0; j <= n; j++) {
            //mg[i][j] *= 10000;
        }

    }



    for(int la = n - 1; la >= 2; la--) {
        int baz;
        for(int i = 1; i < n; i++) {
            if(mg[i][la] != 0 && !viz[i]) {
                baz = i;
            }
        }
        viz[baz] = 1;
        for(int i = 1; i < n; i++) {
            if(!viz[i]) {
                sterge(i, baz, la);
            }
        }
/*
        for(int i = 1; i < n; i++) {
            for(int j = 0; j <= n; j++) {
                printf("%.3f ", mg[i][j]);
            }
            printf("\n");
        }
        printf("\n\n");
*/
    }




    for(int i = 1; i < n; i++) {
        int f = 0;
        for(int j = 1; j <= n; j++) {
            if(j != 1) {
                if(mg[i][j] != 0) {
                    f = 1;
                    break;
                }
            } else {
                if(mg[i][j] == 0) {
                    f = 1;
                    break;
                }
            }
        }
        if(f == 0) {
            fprintf(we, "%f", (mg[i][0] / mg[i][1]));
            break;
        }
    }

    fclose(re);
    fclose(we);


    return 0;
}