#include <bits/stdc++.h>
using namespace std;;
using ll = long long;
using ull = unsigned long long;
using ld = long double;
using uint = unsigned int;
const double EPS = 1e-8;
const int INF = 0x3F3F3F3F;
const ll LINF = 46 * ll(1e17);
const int MOD = 1e9 + 7;
const int maxn = 1e5 + 25;

struct dsu_undo {
    vector<int> e;
    int cnt_cc, cnt_size_one;
    vector<pair<int, int>> st;
    vector<int> st2, st3;
    dsu_undo(int n): e(n, -1), cnt_cc(n), cnt_size_one(n) { }
    int size(int x) { return -e[find(x)]; }
    int find(int x) { return e[x] < 0 ? x : find(e[x]); }
    int time() { return st.size(); }
    void rollback(int t) {
        for (int i = time(); i-- > t;) {
            e[st[i].first] = st[i].second;
            cnt_size_one = st2[i];
            cnt_cc = st3[i];
        }
        st.resize(t);
        st2.resize(t);
        st3.resize(t);
    }
    bool join(int a, int b) {
        a = find(a), b = find(b);
        if (a == b)
            return false;
        if (e[a] > e[b]) swap(a, b);
        st.push_back({a, e[a]});
        st.push_back({b, e[b]});
        st2.push_back(cnt_size_one);
        st2.push_back(cnt_size_one);
        st3.push_back(cnt_cc);
        st3.push_back(cnt_cc);
        cnt_size_one -= (size(a) == 1) + (size(b) == 1);
        cnt_cc--;
        e[a] += e[b]; e[b] = a;
        return true;
    }
};
// cnt_cc, cnt_size_one, size()
int l[maxn];
int ord[maxn];
int mod[maxn];
vector<int> lgraph[maxn], rgraph[maxn];
signed main() { ios::sync_with_stdio(0); cin.tie(0);
    int n, m;
    cin >> n >> m;
    dsu_undo ldsu(n), rdsu(n);
    for(int i = 0; i < n; ++i) {
       cin >> l[i]; 
       ord[i] = i;
    }
    sort(ord, ord + n, [](int a, int b) {
        return l[a] < l[b];
    });
    for(int i = 0; i < m; ++i) {
        int u, v;
        cin >> u >> v;
        --u, --v;
        if(l[u] < l[v]) swap(u, v);
        lgraph[u].push_back(v);
        rgraph[v].push_back(u);
    }
    for(int i = n - 1; i >= 0; --i) {
        int u = ord[i];
        for(auto v : rgraph[u]) {
            mod[i] += rdsu.join(u, v); 
        }
    }
    for(int i = 0; i < n - 1; ++i) {
        int u = ord[i];
        for(auto v : lgraph[u]) {
            ldsu.join(u, v);
        }
        auto t = rdsu.time();
        rdsu.rollback(t - 2 * mod[i]);
        if(l[ord[i + 1]] == l[ord[i]]) continue;
        int lcntcc = ldsu.cnt_cc - (n - i - 1);
        int rcntcc = rdsu.cnt_cc - (i + 1);
        int lcntone = ldsu.cnt_size_one - (n - i - 1);
        int rcntone = rdsu.cnt_size_one - (i + 1); 
        if(i + 1 < rcntcc || (n - i - 1) < lcntcc) continue;
        int edge = lcntcc - lcntone + rcntcc - rcntone - 1;
        int lleft = (i + 1) - lcntone - edge;
        int rleft = (n - i - 1) - rcntone - edge;
        if(((lleft >= rcntone) || (rleft >= lcntone)) && (lleft >= 0 && rleft >= 0)) {
            cout << l[u] << '\n';
            return 0;
        }
    }
    cout << "-1\n";
    return 0;
}