#include<bits/stdc++.h>
#define il inline
#define LL long long
#define _(d) while(d(isdigit(ch=getchar())))
using namespace std;
const int N=1e5+5;
bool f[N];
LL ans,dist[N],S;
int dfn[N],id,sz[N],mx[N],sum[N],out[N],rt,a[N];
int n,k,head[N],ne[N<<1],to[N<<1],w[N<<1],cnt;
il int read(){int x,f=1;char ch;_(!)ch=='-'?f=-1:f;x=ch^48;_()x=(x<<1)+(x<<3)+(ch^48);return f*x;
}
il void insert(int x,int y,int z){ne[++cnt]=head[x];head[x]=cnt;to[cnt]=y;w[cnt]=z;
}
il void dfs1(int x,int fa){dfn[x]=++id;sz[x]=f[x];sum[id]=sum[id-1]+f[x];if(f[x])S+=dist[x];for(int i=head[x];i;i=ne[i]){if(to[i]==fa)continue;dist[to[i]]=dist[x]+w[i];dfs1(to[i],x);sz[x]+=sz[to[i]];mx[x]=max(mx[x],sz[to[i]]);}mx[x]=max(mx[x],k-sz[x]);out[x]=id;
}
il void dfs2(int x,int fa){if(mx[x]*2<=k&&ans<S)ans=S,rt=x;for(int i=head[x];i;i=ne[i]){if(fa==to[i])continue;int tot=sum[out[to[i]]]-sum[dfn[to[i]]-1];S+=1ll*(k-(tot<<1))*w[i];dfs2(to[i],x);S-=1ll*(k-(tot<<1))*w[i];}
}
int tt=0;
vector<int> v[N];
struct node{int x,d,id;bool operator<(const node&t1)const{return d<t1.d;}
};
priority_queue<node> q;
il void dfs3(int x,int fa){if(f[x])v[tt].push_back(x);for(int i=head[x];i;i=ne[i]){if(fa==to[i])continue;dfs3(to[i],x);}
}
int main()
{n=read();k=read();for(int i=1;i<n;i++){int x=read(),y=read(),z=read();insert(x,y,z);insert(y,x,z);}for(int i=1;i<=k;i++)a[i]=read(),f[a[i]]=1;dfs1(1,0);dfs2(1,0);if(f[rt])v[++tt].push_back(rt);for(int i=head[rt];i;i=ne[i])++tt,dfs3(to[i],rt);for(int i=1;i<=tt;i++){int x=v[i].size();if(!x)continue;q.push((node){v[i][x-1],x-1,i});}for(int i=1;i<=(k>>1);i++){node a=q.top();q.pop();node b=q.top();q.pop();printf("%d %d\n",a.x,b.x);if(a.d>=1)q.push((node){v[a.id][a.d-1],a.d-1,a.id});if(b.d>=1)q.push((node){v[b.id][b.d-1],b.d-1,b.id});}return 0;
}