#include<bits/stdc++.h>
#define all(x) (x).begin(), (x).end()
#define fi first
#define se second
#define lowbit(x) ((x) & (-x))
using i64 = long long;
using pii = std::pair<int, int>;
void solve()
{
    int n, m;
    std::cin >> n >> m;
    std::vector<int> a(n + 1);
    for (int i = 1; i <= n; ++ i) {
        std::cin >> a[i];
    }
    std::vector<int> d(n + 1);
    while (m --) {
        int u, v;
        std::cin >> u >> v;
        d[u] ++;
        d[v] ++;
    }
    if (n == 1) {
        std::cout << a[1] << '\n';
        return;
    }
    int ans = 0;
    for (int i = 1; i <= n; ++ i) {
        if (d[i] >= 2) {
            ans = std::max(ans, a[i]);
        }
    }
    std::cout << ans << '\n';
}
int main()
{
    std::cin.tie(nullptr);
    std::cout.tie(nullptr);
    std::ios::sync_with_stdio(false);
    int T = 1;
    //std::cin >> T;
    while (T --) solve();
    return 0;
}