#include <bits/stdc++.h>
using namespace std;
#define int long long

void QAQ() {
    int n, m;
    cin >> n >> m;

    vector<int> a(n + 1);

    for (int i = 1; i <= n; i++) {
        cin >> a[i];
    }

    vector adj(n + 1, vector<int>());

    for (int i = 1, u, v; i <= m; i++) {
        cin >> u >> v;
        adj[u].emplace_back(v), adj[v].emplace_back(u);
    }

    map<int, vector<int>> mp;
    int ans = 0;

    for (int i = 1; i <= n; i++) {
        if (adj[i].size() == 0) {
            ans = max(ans, a[i]);
        } else if (adj[i].size() == 1) {
            mp[adj[i][0]].emplace_back(a[i]);
        } else {
            ans = max(ans, a[i]);
        }
    }

    for (auto & [x, cnt] : mp) {
        if (cnt.size() >= 2) {
            sort(cnt.begin(), cnt.end(), greater<>());
            ans = max(ans, cnt[1]);
        }
    }

    cout << ans << "\n";
}

signed main() {
    cin.tie(0) -> sync_with_stdio(0);
    int t = 1;
    // cin >> t;
    for(cout << fixed << setprecision(12); t--; QAQ());
}