#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cmath>
#include<vector>
using namespace std;
#define maxm 200005
#define maxn 10005
const long double eps=1e-9;
 
int n,m,cnt,top;
int pos[maxn],stack[maxn];
bool instack[maxn];
long long tot;
long double ans,K[1000][1000],T[1000][1000];
 
vector<int> v[maxn];
 
struct edge{
    int from,to,dis,val;
    bool operator <(const edge &a)const{return dis<a.dis;}
}e[maxm];
 
inline int read(){
    int x=0;char ch=getchar();
    for (;ch<‘0‘||ch>‘9‘;ch=getchar());
    for (;ch>=‘0‘&&ch<=‘9‘;ch=getchar()) x=x*10+ch-‘0‘;
    return x;
}
 
struct union_find_set{
    int fa[maxn];
    int find(int x){return fa[x]==x?x:fa[x]=find(fa[x]);}
}u1,u2;
 
long long gauss(){
    int t,n=cnt-1,f=1;long double ans=1;
    for (int i=1;i<n;i++){
        for (t=i;t<=n;t++) if (fabs(K[t][i])>eps) break;if (t>n) return 0;
        if (t!=i){for (int j=1;j<=n;j++) swap(K[i][j],K[t][j]);f=-f;}
        for (int j=i+1;j<=n;j++)
            if (fabs(K[j][i])>eps){
                long double t=K[j][i]/K[i][i];
                for (int k=i;k<=n;k++) K[j][k]-=K[i][k]*t;
            }
    }
    for (int i=1;i<=n;i++) ans=ans*K[i][i];
    return round(ans*f);
}
 
void add(int x,int y,int val){
    K[x][y]-=val,K[y][x]-=val;
    K[x][x]+=val,K[y][y]+=val;
}
 
int main(){
    n=read(),m=read();
    for (int i=1;i<=m;i++) e[i].from=read(),e[i].to=read(),e[i].dis=read(),e[i].val=read();
    for (int i=1;i<=n;i++) u1.fa[i]=u2.fa[i]=i; sort(e+1,e+m+1);
    for (int i=1,l=1;i<=m+1;i++){
        int x=u1.find(e[i].from),y=u1.find(e[i].to);
        if (x!=y){int u=u2.find(x),v=u2.find(y);if (u!=v) u2.fa[u]=v;}
        if (e[i].dis!=e[i+1].dis){
            for (int j=l;j<=i;j++){
                int x=u1.find(e[j].from),y=u1.find(e[j].to);
                if (x==y) continue; int u=u2.find(x);
                if (!instack[u]) stack[++top]=u,instack[u]=1;
            }
            while (top){
                instack[stack[top]]=0,cnt=0;
                for (int j=l;j<=i;j++){
                    int x=u1.find(e[j].from),y=u1.find(e[j].to);
                    if (x==y) continue; int u=u2.find(x);
                    if (u==stack[top]){
                        if (!pos[x]) pos[x]=++cnt;
                        if (!pos[y]) pos[y]=++cnt;
                        add(pos[x],pos[y],1);
                    }
                }
                for (int a=1;a<=cnt;a++)
                    for (int b=1;b<=cnt;b++)
                        T[a][b]=K[a][b];
                tot=gauss();
                for (int a=1;a<=cnt;a++)
                    for (int b=1;b<=cnt;b++)
                        K[a][b]=T[a][b];
                for (int j=l;j<=i;j++){
                    int x=u1.find(e[j].from),y=u1.find(e[j].to);
                    if (x==y) continue; int u=u2.find(x);
                    if (u==stack[top]){
                        for (int a=1;a<=cnt;a++)
                            for (int b=1;b<=cnt;b++)
                                T[a][b]=K[a][b];
                        add(pos[x],pos[y],-1);
                        long long tmp=gauss();
                        for (int a=1;a<=cnt;a++)
                            for (int b=1;b<=cnt;b++)
                                K[a][b]=T[a][b];
                        ans+=1.0*(tot-tmp)/tot*e[j].val;
                    }
                }
                for (int j=l;j<=i;j++){
                    int x=u1.find(e[j].from),y=u1.find(e[j].to);
                    if (x==y) continue;pos[x]=pos[y]=0;
                }
                for (int j=1;j<=cnt;j++)
                    for (int k=1;k<=cnt;k++)
                        K[j][k]=0;
                top--;
            }
            for (int j=l;j<=i;j++){
                int x=u1.find(e[j].from),y=u1.find(e[j].to);
                if (x==y) continue;u1.fa[x]=y;
            }
            l=i+1;
        }
    }
    printf("%.5lf",(double)ans);
    return 0;
}