#include<bits/stdc++.h>
#define maxN 105
#define maxM 5005
#define eps 0.00000001
using namespace std;

long double a[maxN][maxN];
typedef struct tip
{
    int x,y,c;
};
int seen[maxN],cnt;
tip edge[maxM];
vector<pair<int,int> > v[maxN];
inline void dfs(int nod)
{
    seen[nod]=++cnt;
    for(vector<pair<int,int> >::iterator it=v[nod].begin();it!=v[nod].end();it++)
    {
        if(!seen[it->first]) dfs(it->first);
    }
}
int n,m,x,y,c;
long double sol[maxN],ans;
ifstream fin("flux.in");
ofstream fout("flux.out");
int main()
{
   // freopen("flux.in","r",stdin);
 //   freopen("flux.out","w",stdout);
  //  scanf("%d%d",&n,&m);
    fin>>n>>m;
    for(int i=1;i<=m;i++)
    {
      //  scanf("%d%d%d",&x,&y,&c);
        fin>>x>>y>>c;
        v[x].push_back({y,c});
        v[y].push_back({x,c});
        edge[i]={x,y,c};
    }
    dfs(1);
    /*if(!seen[n])
    {
       // printf("%lf\n",0.0);
        fout<<'0.0'<<'\n';
        return 0;
    }*/
    a[1][1]=a[n][n]=1.0;
    a[n][n+1]=1.0;
    //gauss[1][n+1]=1.0;
    sol[n]=1.0;
    for(int i=2;i<n;i++)
    {
      //  if(i==seen[n]) continue;
        a[i][i]=1.0*v[i].size();
        for(vector<pair<int,int> >::iterator it=v[i].begin();it!=v[i].end();it++)
        {
            a[i][it->first]-=1.0;
        }
    }
 //   sol[n]=1.0;
    int i=1,j=1;
    while(i<=n && j<=n)
    {
        int k;
        for(k=i;k<=n;k++)
        {
            if(a[k][j]<-eps || a[k][j]>eps)
                break;
        }
        if(k==(n+1)) //Necunoscuta Libera
        {
            j++;
            continue;
        }
        if(k!=i)
        {
            //Schimbam liniile k si i
            for(int u=1;u<=n+1;u++)
            {
                swap(a[i][u],a[k][u]);
            }
        }
        for(int u=j+1;u<=n+1;u++)
        {
            a[i][u]/=a[i][j];
        }
        a[i][j]=1; //Reducem toata ecuatia de pe linia i ca sefii
        for(int u=i+1;u<=n;u++)
        {
            for(int l=j+1;l<=n+1;l++)
            {
                a[u][l]-=a[u][j]*a[i][l];
            }
            a[u][j]=0; //Practic reducem necunoscuta i din toate ecuatiile
        }
        i++;
        j++;
    }
    for(int i=n;i>0;i--)
    {
        for(int j=1;j<=n+1;j++)
        {
            if(a[i][j]<-eps || a[i][j]>eps)
            {
            if(j==n+1)
            {
                printf("Imposibil\n");
                return 0;
            }
            sol[j]=a[i][n+1];
            for(int k=j+1;k<=n;k++)
                sol[j]-=sol[k]*a[i][k];
            break;
            }
        }
    }
    long double coef=1E60;
  //  cerr<<eps<<'\n';
    for(int i=1;i<=m;i++)
    {
        if(edge[i].x && edge[i].y) coef=min(coef,(1.0*edge[i].c)/fabs(sol[edge[i].y]-sol[edge[i].x]));
    }
    for(vector<pair<int,int> >::iterator it=v[1].begin();it!=v[1].end();it++)
    {
        ans=ans+(sol[it->first]*coef);
    }
    fout<<setprecision(10)<<ans<<'\n';
    return 0;
}