#include<bits/stdc++.h>
using namespace std;

#define x first
#define y second 
#define Yes cout << "Yes\n"
#define No cout << "No\n"
#define YES cout << "YES\n"
#define NO cout << "NO\n"
#define ls u << 1
#define rs u << 1 | 1
#define all(x) x.begin(),x.end()
#define i128 __int128
#define int long long
#define Genshin_Impact return
#define Starts 0
#define _o_o_ return
#define o_o_o return

inline int gcd(int a, int b) {return b > 0 ? gcd(b, a % b) : a;}
inline int lowbit(int x) {return x & (-x);}
int qmi(int a, int b, int mod){int res = 1;while(b) {if(b & 1) res = res * a % mod;a = a * a % mod;b >>= 1;}return res;}
// inline i128 read(){i128 x = 0, f = 1;char ch = getchar();while(ch < '0' || ch > '9'){if(ch == '-')f = -1;ch = getchar();}while(ch >= '0' && ch <= '9'){x = x * 10 + ch - '0';ch = getchar();}return x * f;}
// inline void print(i128 x){if(x < 0){putchar('-');x = -x;}if(x > 9)print(x / 10);putchar(x % 10 + '0');}

typedef long long ll;
typedef pair<int, int> PII;
typedef pair<double, PII> PIII;



const int N = 5e5 + 10, logn = 21, inf = 1e18, mod = 998244353, M = 2e6 + 10;
const int P = 131;
#define ull unsigned long long

int n, m; 
vector<int>v;
int a[N], b[N], d[N], mx = 0;
PII p[N];
void solve()
{
    // 选一个不是叶子的最大值
    // 或者次大叶子
    cin >> n >> m;
    for(int i = 1; i <= n; i ++) cin >>  a[i], b[i] = a[i];
    for(int i = 1; i <= m; i ++) {
        int u, v; cin >> u >> v;
        d[u] ++, d[v] ++;
        p[i] = {u, v};
    }
    if(n == 1) {
        cout << a[1] << '\n';
        return;
    }
    // 对于一条边上的两个点，度大于2就可以每个点都做最后的点，否则就是次大
    sort(b + 1, b + n + 1);
    int mx = 0;
    for(int i = 1; i <= m; i ++) 
        if(d[p[i].x] == 1) {
            mx = max(mx, a[p[i].y]);
            // 或者除去这个值的次大值
            if(a[p[i].y] == b[n - 2]) {
                if(a[p[i].x] >= b[n - 1])
                    mx = max(mx, b[n - 1]);
                else mx = max(mx, a[p[i].x]);
            }
            else {
                if(a[p[i].x] >= b[n - 1]) mx = max(mx, b[n - 2]);
                else mx = max(mx, a[p[i].x]);
            }
        }
        else if(d[p[i].y] == 1) {
            mx = max(mx, a[p[i].x]);
            if(a[p[i].x] == b[n - 2]) {
                if(a[p[i].y] >= b[n - 1])
                    mx = max(mx, b[n - 1]);
                else mx = max(mx, a[p[i].y]);
            }
            else {
                if(a[p[i].y] >= b[n - 1]) mx = max(mx, b[n - 2]);
                else mx = max(mx, a[p[i].y]);
            }
        }
        else mx = max(mx, max(a[p[i].x], a[p[i].y]));
    cout << mx << '\n';
}

signed main()
{
    ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
    int t = 1;
    // cin >> t;
    while (t--)
        solve();
    Genshin_Impact Starts;
}