#include<bits/stdc++.h>
using namespace std;
struct node
{
	int l,r;
	vector<tuple<int,int,int>> eg;
	node *lson,*rson;
}*root,pool[7777777];
int top;
node *build(int l,int r)
{
	node *ret=&pool[top++];
	ret->l=l;ret->r=r;
	return ret;
}
void ins(node *cur,int l,int r,const tuple<int,int,int> &eg)
{
//	auto [x,y,z]=eg;
//	cerr<<"ins "<<l<<' '<<r<<' '<<x<<' '<<y<<' '<<z<<endl;
	
	if(cur->l==l and cur->r==r)
	{
		cur->eg.push_back(eg);
		return;
	}
	int mid=(cur->l+cur->r)/2;
	if(mid>=r)
	{
		if(not cur->lson)cur->lson=build(cur->l,mid);
		ins(cur->lson,l,r,eg);
	}
	else if(mid+1<=l)
	{
		if(not cur->rson)cur->rson=build(mid+1,cur->r);
		ins(cur->rson,l,r,eg);
	}
	else
	{
		if(not cur->lson)cur->lson=build(cur->l,mid);
		if(not cur->rson)cur->rson=build(mid+1,cur->r);
		ins(cur->lson,l,mid,eg);
		ins(cur->rson,mid+1,r,eg);
	}
}
int pa[111111],sz[111111];
int find(int x){return pa[x]?find(pa[x]):x;}
int cntv[2];
int cnte[2]={0,0};
vector<int> sr;
bool check(int mid)
{
	while(sr.back()<=mid)sr.pop_back(),cntv[1]--,cntv[0]++;
//	cerr<<"check "<<mid<<' '<<cntv[0]<<' '<<cntv[1]<<' '<<cnte[0]<<' '<<cnte[1]<<endl;
	int neede=cntv[0]+cntv[1]-cnte[0]-cnte[1]-1;
	return cntv[0]>=neede and cntv[1]>=neede;
}
void solve(node *cur)
{
//	cerr<<"dfs "<<cur->l<<' '<<cur->r<<endl;
	vector<pair<int*,int>> mod;
	int tmp[2]={cnte[0],cnte[1]};
	for(auto [u,v,ty]:cur->eg)
	{
		int pu=find(u),pv=find(v);
		if(pu==pv)continue;
//		cerr<<"merge "<<pu<<' '<<pv<<endl;
		if(sz[pu]>sz[pv])swap(pu,pv);
		mod.emplace_back(&pa[pu],pa[pu]);
		pa[pu]=pv;
		mod.emplace_back(&sz[pv],sz[pv]);
		sz[pv]+=sz[pu];
		cnte[ty]++;
	}
//	cerr<<"?? "<<endl;
	int mid=(cur->l+cur->r)/2;
	if(cur->lson)solve(cur->lson);
	else if(check(cur->l))
	{
		cout<<cur->l<<endl;
		exit(0);
	}
	if(cur->rson)solve(cur->rson);
	else if(check(mid+1))
	{
		cout<<mid+1<<endl;
		exit(0);
	}
	reverse(mod.begin(),mod.end());
	for(auto [pt,x]:mod)*pt=x;
	cnte[0]=tmp[0],cnte[1]=tmp[1];
}
int w[111111],u[111111],v[111111];
int main()
{
	ios_base::sync_with_stdio(false);
	int n,m;
	cin>>n>>m;
	for(int i=1;i<=n;i++)sz[i]=1;
	cntv[1]=n;
	int minn=1e9,maxx=0;
	for(int i=1;i<=n;i++)
	{
		cin>>w[i];
		minn=min(minn,w[i]);
		maxx=max(maxx,w[i]);
		sr.push_back(w[i]);
	}
	sort(sr.begin(),sr.end(),greater<int>());
	if(minn==maxx)
	{
		cout<<-1<<endl;
		return 0;
	}
	
	root=build(minn,maxx-1);
	for(int i=1;i<=m;i++)
	{
		cin>>u[i]>>v[i];
		if(w[u[i]]>w[v[i]])swap(u[i],v[i]);
		if(minn<w[u[i]])ins(root,minn,w[u[i]]-1,{u[i],v[i],1});
		if(w[v[i]]<maxx)ins(root,w[v[i]],maxx-1,{u[i],v[i],0});
	}
	solve(root);
	cout<<-1<<endl;
	return 0;
}