#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define pb emplace_back
#define AI(i) begin(i), end(i)
template<class T> bool chmax(T &a, T b) { return a < b && (a = b, true); }
template<class T> bool chmin(T &a, T b) { return b < a && (a = b, true); }
#ifdef KEV
#define DE(args...) kout("{ " + string(#args) + " } = ", args)
void kout() { cerr << endl; }
template<class T, class ...U> void kout(T a, U ...b) { cerr << a << ' ', kout(b...); }
#else
#define DE(...) 0
#define debug(...) 0
#endif

const int MAX_N = 300010, inf = 1e9;

struct dsu {
    vector<int> g, sz;
    dsu(int n) : g(n), sz(n, 1) {
        iota(AI(g), 0);
    }
    int F(int i) { return i == g[i] ? i : g[i] = F(g[i]); }
    bool M(int a, int b) {
        a = F(a), b = F(b);
        if (a == b) return false;
        if (sz[a] < sz[b]) swap(a, b);
        return sz[a] += sz[b], g[b] = a, true;
    }
};
int32_t main() {
    ios_base::sync_with_stdio(0), cin.tie(0);

    int n, m;
    cin >> n >> m;
    vector<vector<int>> edge(n+1);

    vector<int> l(n);

    for (int &i : l) cin >> i;

    for (int a, b, i = 0;i < m;++i) {
        cin >> a >> b, --a, --b;
        edge[a].pb(b), edge[b].pb(a);
    }

    vector<int> lcnt(n+10), rcnt(n+10);

    vector<int> id(n); iota(AI(id), 0); sort(AI(id), [&](int x, int y) {
        return l[x] < l[y];
    });

    vector<int> cl(l); sort(AI(cl));

    {
        int sz = 0;
        dsu g(n + 10);
        for (int i = 0;i < n;++i) {
            int x = id[i];
            ++sz;
            for (int j : edge[x]) if (l[j] <= l[x])
                sz -= g.M(j, x);

            if (i==n-1 || cl[i+1] > cl[i]) {
                lcnt[i] = sz;
            }
            else lcnt[i] = inf;
        }
    }

    {
        int sz = 0;
        dsu g(n + 10);
        for (int i = n-1;i >= 0;--i) {
            int x = id[i];
            DE(x+1);
            ++sz;
            for (int j : edge[x]) if (l[j] >= l[x]) {
                sz -= g.M(j, x);
                DE(x+1, j+1, l[j], l[x]);
            }

            if (i==0 || cl[i]>cl[i-1]) {
                rcnt[i] = sz;
            }
            else rcnt[i] = inf;
        }
    }
    for (int i =0 ;i < n;++i) DE(i, lcnt[i], rcnt[i]);

    for (int i = 0;i+1 < n;++i) {
        if (cl[i+1] > cl[i]) {
            if (min(i+1, n-i-1) >= lcnt[i]+rcnt[i+1]-1) {
                DE(i, min(i+1, n-i-1), lcnt[i], rcnt[i+1]);
                cout << cl[i] << '\n';
                return 0;
            }
        }
    }
    cout << -1 << '\n';

}