#include <bits/stdc++.h>
using namespace std;
int main() {
	ios::sync_with_stdio(false), cin.tie(0);
	int n, m; cin >> n >> m;
	vector<int> a(n);
	for(int &x : a) cin >> x;
	vector<vector<int>> G(n);
	for(int i = 0; i < m; i ++) {
		int u, v; cin >> u >> v;
		G[-- u].emplace_back(-- v);
		G[v].emplace_back(u);
	}
	vector<int> id(n);
	iota(id.begin(), id.end(), 0);
	sort(id.begin(), id.end(), [&] (int x, int y) {return a[x] < a[y];});
	struct dsu_t {
		vector<int> fa;
		dsu_t(int n) : fa(n) {iota(fa.begin(), fa.end(), 0);}
		int find(int x) {return fa[x] == x ? x : fa[x] = find(fa[x]);}
		bool merge(int u, int v) {
			u = find(u), v = find(v);
			return u != v ? fa[u] = v, 1 : 0;
		}
	};
	
	auto solve = [&] {
		dsu_t dsu(n);
		vector<int> ans(n), vis(n);
		int cnt = 0;
		for(int i = 0; i < n; i ++) {
			int u = id[i];
			vis[u] = 1;
			for(auto v : G[u]) if(vis[v]) {
				cnt += dsu.merge(u, v);
			}
			ans[i] = cnt;
		}
		return ans;
	};
	auto x = solve();
	reverse(id.begin(), id.end());
	auto y = solve();
	reverse(y.begin(), y.end());
	reverse(id.begin(), id.end());
	for(int i = 0; i < n - 1; i ++) if(a[id[i]] != a[id[i + 1]]) {
		if(n - 1 - x[i] - y[i + 1] <= min(i + 1, n - i - 1)) {
			cout << a[id[i]] << '\n';
			exit(0);
		}
	}
	cout << -1 << '\n';
	return 0;
}