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

const int N = 100005;

vector<int> adj[N];
int n, m, a[N], id[N];

int f[N], sz[N];
int find(int x) {
    return f[x] == x ? x : f[x] = find(f[x]);
}

// size = 1: cnt1
// size > 1: cnt2
// total dot: tot
// total comp: cnt1 + cnt2
struct Info {
    int cnt1, cnt2, tot;    
} pre[N], suf[N];

bool check(Info L, Info R) {
    int k1 = L.cnt1 + L.cnt2, k2 = R.cnt1 + R.cnt2;
    
//    printf("now L = (cnt1 = %d, cnt2 = %d, tot = %d)\n", L.cnt1, L.cnt2, L.tot);
//    printf("now R = (cnt1 = %d, cnt2 = %d, tot = %d)\n", R.cnt1, R.cnt2, R.tot);

    if (k2 == 1) swap(L, R), swap(k1, k2);
    if (k1 == 1) {
        return L.tot >= k2;
    } else {
        if (!L.cnt2 || !R.cnt2) return false;
        if (L.tot < k2) return false;
        if (R.tot < k1) return false;
        if (L.tot - k1 < R.cnt1) return false;
        if (R.tot - k2 < L.cnt1) return false;
        return true;
    } 
}

int main() {
    scanf("%d%d", &n, &m);
    for (int i = 1; i <= n; i++) {
        scanf("%d", &a[i]);
        id[i] = i;
    }
    sort(id + 1, id + n + 1, [&](int i, int j) {
        return a[i] < a[j];
    });
    static int rk[N];
    for (int i = 1; i <= n; i++) rk[id[i]] = i;
    for (int i = 1; i <= m; i++) {
        int u, v; scanf("%d%d", &u, &v);
        adj[u].push_back(v);
        adj[v].push_back(u);
    }
    
    for (int i = 1; i <= n; i++) {
        f[i] = i, sz[i] = 1;
    }
    for (int x = 1; x <= n; x++) {
        int u = id[x];
        pre[x] = pre[x - 1];
        pre[x].tot++, pre[x].cnt1++;
        for (auto v: adj[u]) {
            if (rk[v] >= rk[u]) continue;
            if (find(u) == find(v)) continue;
            int fu = find(u), fv = find(v);
            pre[x].cnt1 -= (sz[fu] == 1) + (sz[fv] == 1);
            pre[x].cnt2 -= (sz[fu] > 1) + (sz[fv] > 1);
            sz[fv] += sz[fu], f[fu] = fv;
            pre[x].cnt1 += (sz[fv] == 1);
            pre[x].cnt2 += (sz[fv] > 1);
        }
    }
    for (int i = 1; i <= n; i++) {
        f[i] = i, sz[i] = 1;
    }
    for (int x = n; x >= 1; x--) {
        int u = id[x];
        suf[x] = suf[x + 1];
        suf[x].tot++, suf[x].cnt1++;
        for (auto v: adj[u]) {
            if (rk[v] <= rk[u]) continue; 
            if (find(u) == find(v)) continue;
            int fu = find(u), fv = find(v);
            suf[x].cnt1 -= (sz[fu] == 1) + (sz[fv] == 1);
            suf[x].cnt2 -= (sz[fu] > 1) + (sz[fv] > 1);
            sz[fv] += sz[fu], f[fu] = fv;
            suf[x].cnt1 += (sz[fv] == 1);
            suf[x].cnt2 += (sz[fv] > 1);
        }
    }
    
    for (int x = 1; x < n; x++) {
        if (a[id[x]] != a[id[x + 1]]) {
//            printf("current debug %d\n", a[id[x]]);
            if (check(pre[x], suf[x + 1])) {
                printf("%d\n", a[id[x]]);
                return 0;
            }
        }
    }
    puts("-1");
    return 0;
}