#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define rep(i,l,r) for(ll i=l;i<=r;++i)
#define rep_(i,r,l) for(ll i=r;i>=l;--i)
const ll N = 2e5 + 7;
const ll P = 1e9 + 7;

ll a[N], in[N];
void solve() {
	ll n, m; cin >> n >> m;
	rep(i, 1, n) cin >> a[i];
	if (n == 1) { cout << a[1] << endl; return; }
	rep(i, 1, m) {
		ll u, v; cin >> u >> v;
		in[u]++, in[v]++;
	}
	ll ans = 0;
	rep(i, 1, n) {
		if (in[i] < 2) continue;
		ans = max(ans, a[i]);
	}
	cout << ans << endl;
}
int main() {
	//cout << fixed << setprecision(0) << 0.500 << endl;
	ios::sync_with_stdio(0);
	cin.tie(0);
	int T(1);
	//cin >> T;
	while (T--) {
		solve();
	}
}