#include <bits/stdc++.h>
#define int long long

using namespace std;

const int N = 1e5 + 10;

int n, m;
int a[N];
vector<int> g[N];
int d[N];
int ans;

void dfs(int u, int fa)
{
    int v1 = -1, v2 = -1;
    for (auto t : g[u])
    {
        if (t == fa) continue;
        if (a[t] > v1)
        {
            v2 = v1;
            v1 = a[t];
        }
        else if (a[t] > v2) v2 = a[t];
        dfs(t, u);
    }
    ans = max(ans, v2);
}

signed main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);

    cin >> n >> m;
    for (int i = 1; i <= n; i ++ ) cin >> a[i];
    for (int i = 0; i < m; i ++ )
    {
        int u, v;
        cin >> u >> v;
        d[u] ++ , d[v] ++ ;
    }
    if (n == 1)
    {
        cout << 1 << '\n';
        return 0;
    }
    for (int i = 1; i <= n; i ++ )
    {
        if (d[i] != 1) ans = max(ans, a[i]);
    }
    dfs(1, -1);
    cout << ans << '\n';
    return 0;
}