#include<cstdio>
#include<algorithm>
#include<cstring>
#define re register
#define maxn 2000005
using namespace std;

inline int read() {
	int s=0,f=1;
	char ch=getchar();
	while(ch<'0'||ch>'9') {
		if(ch=='-')f=-1;
		ch=getchar();
	}
	while(ch>='0'&&ch<='9'){
		s=(s<<3)+(s<<1)+ch-'0';
		ch=getchar();
	}
	return s*f;
}

int max(int x,int y){
	return x>y?x:y;
}

int n,k,x,y,ans;

struct E{
	int y,nxt;
}edge[maxn];

int head[maxn],tot;

void add(int x,int y){
	edge[++tot].y=y;
	edge[tot].nxt=head[x];
	head[x]=tot;
}

int val[maxn];

int cnt,siz,num;

int tree[maxn];

bool vis[maxn],check[maxn];

void dfs(int x){
	vis[x]=1;
	siz++;
	for(re int i=head[x];i;i=edge[i].nxt){
		int y=edge[i].y;
		if(vis[y])continue;
		if(check[y])dfs(y);
	}
}

int main() {
	freopen("green.in","r",stdin);
	freopen("green.out","w",stdout);
	n=read();
	k=read();
	for(re int i=0;i<n;++i){
		val[i]=read();
	}
	for(re int i=1;i<n;++i){
		x=read();
		y=read();
		add(x,y);
		add(y,x);
	}
	int l=0,r=10000000;
	while(l<=r){
		int mid=(l+r)>>1;
		//printf("*%d *%d *%d\n",l,mid,r);
		cnt=0;num=0;
		memset(check,0,sizeof(check));
		memset(vis,0,sizeof(vis));
		for(re int i=0;i<n;++i){
			if(val[i]>=mid){
				tree[++cnt]=i;
				check[i]=1;
			}
		}
		for(re int i=1;i<=cnt;++i){
			if(!vis[tree[i]]){
				siz=0;
				dfs(tree[i]);
				num=max(num,siz);
			//	printf("siz=%d?\n",siz);
			}
		}
		if(num<=k){
			ans=num;
			r=mid-1;
		}
		else l=mid+1;
	}
	printf("%d\n",ans);
	return 0;
}
/*
*/