#include<bits/stdc++.h>
#define test(i) cout << #i << " "<< i << " " << endl;
#define endl '\n'

using namespace std;
typedef long long ll;

const int INF=0x3f3f3f3f;
const int N=2e5+5;

ll t;
ll w[N],in[N];
vector<ll> G[N],V[N];

void fio(){
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
}

void solve(){
	ll n,m,u,v;
	cin >> n >> m;
	for(int i=1; i<=n; i++)cin >> w[i];
	for(int i=1; i<=m; i++){
		cin >> u >> v;
		in[u]++;
		in[v]++;
		G[v].push_back(u);
		G[u].push_back(v);
	}
	ll ans=0;
	for(int i=1; i<=n; i++){
		if(in[i]<2) continue;
		ans=max(ans,w[i]);
		for(auto j:G[i]){
			if(in[j]<2) V[i].push_back(j);
		}
	}
	for(int i=1; i<=n; i++){
		ll fir=0,sec=0;
		for(auto j:V[i]){
			if(fir<=w[j]){
				sec=fir;
				fir=w[j];
			}
			else if(sec<=w[j]){
				sec=w[j];
			}
		}
		ans=max(ans,sec);
	}
	cout << ans << endl;
}

signed main()
{
	//fio();
	//cin >> t;
	t=1;
	while(t--){
		solve();
	}
	return 0;
}