#include<bits/stdc++.h>
using namespace std;
inline int read()
{
	int x=0,f=1;char ch=getchar();
	while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
	while(ch>='0'&&ch<='9'){x=x*10-48+ch;ch=getchar();}
	return x*f;
}
const int maxn=2005;
struct Edge
{
	int y,nxt;
}e[maxn<<1];
struct W
{
	int w,id;
}w[maxn];
int tot,head[maxn];
int n,k,ans,we[maxn];
bool vis[maxn];
void add(int x,int y)
{
	e[++tot].y=y;e[tot].nxt=head[x];head[x]=tot;
}
bool cmp(W a,W b)
{
	return a.w>b.w;
}
bool dfs(int x,int limit,int num,int g)
{
	if(num==g)return 1;
	for(int i=head[x],y;i;i=e[i].nxt)
	{
		y=e[i].y;
		if(we[y]<limit)continue;
		if(vis[y])continue;
		num++;
		vis[y]=1;
		if(dfs(y,limit,num,g))return 1;
	}
}
int main()
{
	freopen("green.in","r",stdin);
	freopen("green.out","w",stdout); 
	n=read(),k=read();
	for(int i=0;i<n;i++)
	{
		w[i].id=i;
		we[i]=w[i].w=read();
	}
	sort(w,w+n,cmp);
	for(int i=1;i<n;i++)
	{
		int x=read(),y=read();
		add(x,y);
		add(y,x);
	}
	int djj=0;
	for(int i=1;i<n;i++)
		if(w[i].w==w[0].w)djj=i;
		else break;
	int l=1,r=k,mid;
	bool jd;
	while(l<=r)
	{
		mid=(l+r)>>1;
		jd=0;
		for(int i=0;i<=djj;i++)
		{
			memset(vis,0,sizeof(vis));
			vis[w[i].id]=1;
			if(dfs(w[i].id,w[l].w,1,l))
			{
				jd=1;
				break;
			}
		}
		if(jd)l=mid;
		else r=mid-1;
	}
	cout<<l<<'\n';
	return 0;
}