#include <bits/stdc++.h>
using namespace std;
#define int long long
#define ednl '\n'
const int N = 2e5 + 5;
const int mod = 1e9 + 7;
int n, m, tot, a[N], b[N], pre[N], suf[N], f[N], p[N], s[N];
vector<int> e[N], tr[N];
int find(int x) { return f[x] == x ? x : f[x] = find(f[x]); }
void solve()
{
    cin >> n >> m;
    for (int i = 1; i <= n; i++)
        cin >> a[i], b[++tot] = a[i], f[i] = i;
    sort(b + 1, b + 1 + tot);
    tot = unique(b + 1, b + 1 + tot) - b - 1;
    for (int i = 1; i <= n; i++)
        a[i] = lower_bound(b + 1, b + 1 + tot, a[i]) - b, tr[a[i]].push_back(i);
    for (int i = 1; i <= m; i++)
    {
        int u, v;
        cin >> u >> v;
        pre[min(a[u], a[v])]++;
        suf[max(a[u], a[v])]++;
        e[u].push_back(v);
        e[v].push_back(u);
    }
    for (int i = tot; i >= 1; i--)
        pre[i] += pre[i + 1];
    for (int i = 1; i <= tot; i++)
        suf[i] += suf[i - 1];
    // for (int i = 1; i <= tot; i++)
    //     cout << pre[i] << ' ';
    // cout << endl;
    int cnt = 0, js = 0;
    for (int i = 1; i <= tot; i++)
    {
        for (auto u : tr[i])
        {
            ++cnt;
            for (auto to : e[u])
                if (a[to] <= a[u])
                {
                    int x = find(u), y = find(to);
                    if (x != y)
                    {
                        f[x] = y;
                        cnt--;
                    }
                }
        }
        p[i] = cnt;
    }
    for (int i = 1; i <= n; i++)
        f[i] = i;
    cnt = 0;
    for (int i = tot; i >= 1; i--)
    {
        for (auto u : tr[i])
        {
            ++cnt;
            for (auto to : e[u])
                if (a[to] >= a[u])
                {
                    int x = find(u), y = find(to);
                    if (x != y)
                    {
                        f[x] = y;
                        cnt--;
                    }
                }
        }
        s[i] = cnt;
    }
    cnt = 0, js = 0;
    for (int i = 1; i <= tot; i++)
    {
        for (auto u : tr[i])
            js++;
        // cout << js << ' ' << p[i] << ' ' << s[i] << ' ' << pre[i + 1] << endl;
        if (js && n - js && p[i] - 1 <= pre[i + 1] && s[i + 1] - 1 <= suf[i])
        {
            cout << b[i] << endl;
            return;
        }
    }
    cout << -1 << endl;
}
signed main()
{
    ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
    int t = 1;
    // cin >> t;
    while (t--)
        solve();
    return 0;
}