#include <bits/stdc++.h>
using namespace std;
void solve() {
    int n, m; cin>> n>> m;
    vector<int> a(n), d(n);
    vector<vector<int>> E(n), mx2(n, vector<int>(2));
    for (auto& i : a) cin>> i;
    while (m--) {
        int x, y; cin>> x>> y;x--, y--; 
        d[x]++, d[y]++;
        E[x].push_back(y);
        E[y].push_back(x);
    }
    for (int i = 0; i < n; i++) if (E[i].size() == 1)  {
        int upd = a[i];
        for (auto& j : mx2[E[i][0]]) if (upd >= j) swap(j, upd);
    }
    if (n == 1) cout<< a[0];
    else {
        int ans = -1;
        for (int i = 0; i < n; i++) if (d[i] >= 2) ans = max(ans, max(a[i], mx2[i][1]));
        cout<< ans;
    }
    cout<< '\n';
}
int main() {
    cin.tie(0)->sync_with_stdio(0);
    // int T; cin>> T; while (T--) solve();
    solve();
}