今天晚上思维比较乱，以后再写写吧
#include <iostream>

#include <cstdio>

#include <cstring>

#include <algorithm>

using namespace std;

typedef long long ll;

const int N=1e5+,INF=1e9+;

double eps=1e-;

inline int read(){

    char c=getchar();int x=,f=;

    while(c<''||c>''){if(c=='-')f=-;c=getchar();}

    while(c>=''&&c<=''){x=x*+c-'';c=getchar();}

    return x*f;

}

int n,L,U,a,b;

double w,maxVal,ans;

struct edge{

    int v,ne;

    double w;

}e[N<<];

int h[N],cnt;

inline void ins(int u,int v,double w){

    cnt++;

    e[cnt].v=v;e[cnt].w=w;e[cnt].ne=h[u];h[u]=cnt;

    cnt++;

    e[cnt].v=u;e[cnt].w=w;e[cnt].ne=h[v];h[v]=cnt;

}

int f[N],size[N],all,vis[N],root;

void dfsRt(int u,int fa){

    size[u]=;f[u]=;

    for(int i=h[u];i;i=e[i].ne){

        int v=e[i].v;

        if(vis[v]||v==fa) continue;

        dfsRt(v,u);

        size[u]+=size[v];

        f[u]=max(f[u],size[v]);

    }

    f[u]=max(f[u],all-size[u]);

    if(f[u]<f[root]) root=u;

}

int q[N],head,tail,deep[N];

double val[N],mx[N];

bool visit[N];

void bfs(double g){

    while(head<=tail){

        int u=q[head++];

        for(int i=h[u];i;i=e[i].ne){

            int v=e[i].v;

            if(vis[v]) continue;

            if(!visit[v]){

                visit[v]=;

                q[++tail]=v;

                deep[v]=deep[u]+;

                val[v]=val[u]+e[i].w-g;

            }

        }

    }

}

double c[N];

int m;

bool dp(int n){//printf("dp %d %d\n",n,n+m);

    if(m+n<L) return false;

    head=;tail=;

    int l=max(L-n,),r=U-n;

    for(int i=l;i<=r&&i<=m;i++){//printf("ins %d\n",i);

        while(head<=tail&&c[q[tail]]<c[i]) tail--;

        q[++tail]=i;

    }

    for(int i=n;i>=;i--){//printf("i %d %lf\n",i,mx[i]);

        int l=L-i,r=U-i;//printf("lala %d %d\n",l,r);

        while(head<=tail&&q[head]<l) head++;

        while(head<=tail&&c[r]>c[q[tail]]) tail--;

        q[++tail]=r;

        //printf("qqq %d %d  %lf\n",head,tail,c[q[head]]);

        if(head<=tail&&c[q[head]]+mx[i]>=) return true;

    }

    return false;

}

bool check(int u,double g){//printf("\ncheck %d %lf\n",u,g);

    for(int i=;i<=m;i++) c[i]=-INF;m=;

    for(int i=h[u];i;i=e[i].ne){

        int v=e[i].v;

        if(vis[v]) continue;

                //printf("\nv %d\n",v);

        head=;tail=;

        q[++tail]=v;

        deep[v]=;val[v]=e[i].w-g;

        bfs(g);

        //for(int i=1;i<tail;i++) //printf("%lf ",val[i]);puts("");

        for(int i=;i<=deep[q[tail]];i++) mx[i]=-INF;

        int id;

        for(int i=;i<=tail;i++)

            id=q[i],mx[deep[id]]=max(mx[deep[id]],val[id]),visit[id]=;

        //for(int i=1;i<=maxDeep;i++) printf("mx %d %lf \n",i,mx[i]);

        if(dp(deep[q[tail]])) return true;

        m=max(m,deep[q[tail]]);

        for(int i=;i<=deep[q[tail]];i++) c[i]=max(c[i],mx[i]);

    }

    return false;

}

void dfsSol(int u){//printf("dfsSol %d\n",u);if(u!=1) return;

    vis[u]=;

    double l=ans,r=maxVal;//printf("lr %lf %lf\n\n",l,r);

    while(r-l>eps){

        double mid=(l+r)/;

        if(check(u,mid)) l=mid;

        else r=mid;

    }

    ans=max(ans,l);

    for(int i=h[u];i;i=e[i].ne)

        if(!vis[e[i].v]){

            root=;all=size[e[i].v];

            if(size[e[i].v]<L) continue;

            dfsRt(e[i].v,);

            dfsSol(root);

        }

}

int main(){

    freopen("in","r",stdin);

    //freopen("out","w",stdout);

    n=read();L=read();U=read();

    for(int i=;i<n;i++)

        a=read(),b=read(),w=read(),ins(a,b,w),maxVal=max(maxVal,w);

    root=;f[]=INF;all=n;

    dfsRt(,);

    dfsSol(root);

    printf("%.3lf",ans);

}