#include <bits/stdc++.h>
using namespace std;
using LL = long long;
const LL mod = 998244353;

void solve()
{
    int n, m;
    cin >> n >> m;
    vector<int> a(n + 1);
    vector<int> d(n + 1);
    for(int i = 1; i <= n; i++){cin >> a[i];}
    for(int i = 1; i <= m; i++){
        int x, y;
        cin >> x >> y;
        d[x]++;
        d[y]++;
    }
    if(m == 0){cout << a[1] << "\n"; return ;}
    priority_queue<int> q1;
    priority_queue<int> q2;
    for(int i = 1; i <= n; i++){
        if(d[i] == 1)q1.push(a[i]);
        if(d[i] > 1)q2.push(a[i]);
    }
    int x = q2.top();
    if(q1.top() >= 2){ q1.pop(); x = max(x, q1.top());}
    cout << x << "\n";
}

int main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    solve();
    return 0;
};