# include <cstdio>
# include <cstring>
# include <cstdlib>
# include <iostream>
# include <vector>
# include <queue>
# include <stack>
# include <map>
# include <bitset>
# include <set>
# include <cmath>
# include <algorithm>
using namespace std;
# define lowbit(x) ((x)&(-x))
# define pi acos(-1.0)
# define eps 1e-8
# define MOD 1000000007
# define INF 1000000000
# define mem(a,b) memset(a,b,sizeof(a))
# define FOR(i,a,n) for(int i=a; i<=n; ++i)
# define FO(i,a,n) for(int i=a; i<n; ++i)
# define bug puts("H");
# define lch p<<1,l,mid
# define rch p<<1|1,mid+1,r
# define mp make_pair
# define pb push_back
typedef pair<int,int> PII;
typedef vector<int> VI;
# pragma comment(linker, "/STACK:1024000000,1024000000")
typedef long long LL;
int Scan() {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+ch-'0';ch=getchar();}return x*f;
}
const int N=200005;
//Code begin...struct Edge{int p, next;}edge[N<<1];
int node[N], head[N], cnt=1, dp[N], date[N], siz[N], tag[N], sum, n, K, ans;
bool flag[N];void add_edge(int u, int v){edge[cnt].p=v; edge[cnt].next=head[u]; head[u]=cnt++;}
void dfs1(int x, int fa, int val){siz[x]=1;if (node[x]<val) tag[x]=1, ++sum;if (node[x]<val) flag[x]=true;for (int i=head[x]; i; i=edge[i].next) {int v=edge[i].p;if (v==fa) continue;dfs1(v,x,val); siz[x]+=siz[v]; tag[x]+=tag[v]; flag[x]|=flag[v];}
}
void dfs2(int x, int fa, int val){dp[x]=1;int f=0, s=0;for (int i=head[x]; i; i=edge[i].next) {int v=edge[i].p;if (v==fa) continue;dfs2(v,x,val);if (!flag[v]) dp[x]+=siz[v];else if (node[v]>=val) {if (dp[v]>f) s=f, f=dp[v];else if (dp[v]>s) s=dp[v];}}dp[x]+=f;if (node[x]>=val) {if (tag[x]==sum) ans=max(ans,dp[x]+s+n-siz[x]);else ans=max(ans,dp[x]+s);}
}
bool check(int x){mem(siz,0); mem(dp,0); mem(flag,false); mem(tag,0); sum=ans=0;dfs1(1,0,x); dfs2(1,0,x);return ans>=K;
}
int main ()
{int u, v;scanf("%d%d",&n,&K);FOR(i,1,n) scanf("%d",node+i), date[i]=node[i];FO(i,1,n) scanf("%d%d",&u,&v), add_edge(u,v), add_edge(v,u);sort(date+1,date+n+1);int l=1, r=n+1, mid;while (l<r) {mid=(l+r)>>1;if (l==mid) break;if (check(date[mid])) l=mid;else r=mid;}printf("%d\n",date[l]);return 0;
}