#include <bits/stdc++.h>
#define lowbit(x) (x & -x)
#define int long long
#define lc (p << 1)
#define rc (p << 1 | 1)
using namespace std;
typedef pair<int, int> PII;
mt19937_64 rnd(chrono::steady_clock::now().time_since_epoch().count());
const int N = 2e5 + 5, M = 1e6 + 5, INF = 0x3f3f3f3f, mod = 998244353;

int T = 1, n, m, a[N];
vector<int> e[N];

void solve() {
	
	int ans = 0;
	cin >> n >> m;
	
	for (int i = 1; i <= n; i++) cin >> a[i];
	
	if (n == 1) ans = a[1];
	
	for (int i = 1, u, v; i <= m; i++) {
		cin >> u >> v;
		e[u].push_back(v);
		e[v].push_back(u);
	}
	
	for (int i = 1; i <= n; i++) {
		if (e[i].size() == 1) continue;
		ans = max(ans, a[i]);
		vector<int> arr;
		for (auto & j: e[i])
			if (e[j].size() == 1) arr.push_back(a[j]);
		sort(arr.begin(), arr.end(), greater<int>());
		if (arr.size() > 1) ans = max(ans, arr[1]);
	}
	
	cout << ans << endl;
}
signed main() {
	ios::sync_with_stdio(0);
	cin.tie(0);
//	cin >> T;
	while (T--) solve();
}