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

typedef long long ll;

void solve()
{
    int n, m;
    cin >> n >> m;
    vector<int> a(n + 1);
    for (int i = 1; i <= n; ++i)
        cin >> a[i];

    vector<int> d(n + 1);
    for (int i = 1; i <= m; ++i)
    {
        int u, v;
        cin >> u >> v;
        ++d[u], ++d[v];
    }

    if (n == 1)
    {
        cout << a[1] << '\n';
        return;
    }

    vector<int> f;
    int ans = 0, res = n + 1;
    for (int i = 1; i <= n; ++i)
        if (d[i] > 1)
            ans = max(ans, a[i]);
        else
            f.push_back(a[i]);
    sort(f.begin(), f.end(), greater<int>());
    if (f.size() == 2)
        ans = max(ans, f[1]);
    cout << ans << "\n";
}

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0), cout.tie(0);
    int t = 1;
    // cin >> t;
    while (t--)
    {
        solve();
    }
    return 0;
}