#include<iostream>
#include<cstdio>
#include<cstring>
#include<cmath>
#include<queue>
#include<vector>
#define I inline
#define int long long
using namespace std;

const int N = 100010;
vector<int> q[N];
int n,m,a[N],du[N];

signed main()
{
	cin>>n>>m;
	for(int i=1;i<=n;++i) cin>>a[i];
	if(n==1) {
		cout<<a[1]<<endl;
		return 0;
	}
	for(int i=1;i<=m;++i) {
		int x,y; cin>>x>>y;
		q[x].push_back(y);
		q[y].push_back(x);
		du[x]++; du[y]++;
	}
	int mx1=0,mx2=0,mx3=0;
	for(int i=1;i<=n;++i) {
		if(du[i]>2) {
			mx1=max(mx1,a[i]);
		} else {
			if(a[i]>=mx2) {
				mx3=mx2;
				mx2=a[i];
			} else if(a[i]>mx3) {
				mx3=a[i];
			}
		}
	}
	cout<<max(mx1,mx3)<<endl;
 }  
 
 /*
 7 7 
 1 1 2 3 1 2 1
 1 3
 2 3
 1 3	
 2 4
 2 5
 5 6
 5 7
 
 
 */