#include<iostream>

#include<cstring>

#include<cstdio>

using namespace std;

inline int rd(){

    int ret=,f=;char c;

    while(c=getchar(),!isdigit(c))f=c=='-'?-:;

    while(isdigit(c))ret=ret*+c-'',c=getchar();

    return ret*f;

}

const int MAXN=;

struct Edge{

    int next,to,w;

}e[MAXN<<];

int ecnt,head[MAXN];

inline void add(int x,int y,int w){

    e[++ecnt].next = head[x];

    e[ecnt].to = y;

    e[ecnt].w = w;

    head[x] = ecnt;

}

int n,m;

bool vis[MAXN];

int siz[MAXN];

void getsiz(int x,int pre){

    siz[x]=;

    for(int i=head[x];i;i=e[i].next){

        int v=e[i].to;

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

        getsiz(v,x);

        siz[x]+=siz[v];

    }

}

int mn,root;

void getroot(int x,int pre,int tot){

    int mx=;

    for(int i=head[x];i;i=e[i].next){

        int v=e[i].to;

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

        mx=max(mx,siz[v]);

        getroot(v,x,tot);

    }

    mx=max(mx,tot-siz[x]);

    if(mx<mn) mn=mx,root=x;

}

int s[MAXN],l[MAXN],sav[MAXN];

int f[],g[];

void dfs(int x,int pre,int dis,int len){

    s[++s[]]=dis;l[++l[]]=len;sav[++sav[]]=dis;

    for(int i=head[x];i;i=e[i].next){

        int v=e[i].to;

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

        dfs(v,x,dis+e[i].w,len+);

    }

}

int ans=0x3f3f3f3f;

void dac(int x){

    g[]=;f[]=;sav[]=;mn=n;

    getsiz(x,-);

    getroot(x,-,siz[x]);

    int u=root;vis[u]=;

    for(int i=head[u];i;i=e[i].next){

        int v=e[i].to;

        if(vis[v]) continue;

        l[]=;s[]=;dfs(v,x,e[i].w,);

        for(int j=s[];j>=;j--){

            if(s[j]>m) continue;

            if(f[m-s[j]]) ans=min(ans,g[m-s[j]]+l[j]);

        }

        for(int j=s[];j>=;j--){

            if(s[j]>m) continue;//%%%%Monster_Qi

            f[s[j]]=;

            g[s[j]]=min(g[s[j]],l[j]);

        }

    }

    for(int i=sav[];i>=;i--) if(sav[i]<=m) f[sav[i]]=,g[sav[i]]=0x3f3f3f3f;

    for(int i=head[u];i;i=e[i].next){

        int v=e[i].to;

        if(!vis[v]) dac(v);

    }

}

int main(){

    memset(g,0x3f,sizeof(g));

    n=rd();m=rd();

    int x,y,w;

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

        x=rd();y=rd();w=rd();

        add(x,y,w);add(y,x,w);

    }

    dac();

    if(ans>=0x3f3f3f3f) cout<<-;

    else cout<<ans;

    return ;

}