#include <cstdio>
double c[270][270],a[270];
int n,m,x,y,q,i,j,k;
int main()
{
	freopen("tunel.in","r",stdin);
	freopen("tunel.out","w",stdout);
	scanf("%d%d",&n,&m);
	--n;
	for(i=1;i<=m;i++)
	{
		scanf("%d%d%d",&x,&y,&c);
		++c[x][y];
		++a[x]; 
		++c[y][x];
		++a[y]; 
		c[x][0]+=(double)q;
		c[y][0]+=(double)q;
	}
	for(i=1;i<=n;i++)
	for(j=0;j<=n;j++)
		c[i][j]/=a[i];
	for(i=2;i<=n;i++)
	for(j=1;j<=n;j++)
	for(k=0;k<=n;k++)
		if(j!=i && k!=i)
			c[j][k]+=c[i][k]*1/(1-c[i][i])*c[j][i];
	printf("%lf\n",(1.0/(1.0-c[1][1]))*c[1][0]);
	return 0;
}