#include <bits/stdc++.h>
using namespace std;
#define int long long
typedef long long ll;
typedef unsigned long long ull;
typedef array<int, 3> ar3;
typedef array<int, 4> ar4;
typedef long double ld;
typedef pair<int, int> p11;
typedef pair<string, int> ps1;
typedef pair<ll, ll> p1111;
#define vv vector
#define pb emplace_back
#define IOS ios::sync_with_stdio(false); cin.tie(0); cout.tie(0)
#define fi first
#define se second
#define endl '\n'
#define Endl '\n'
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define per(a, b, c) for(int a = b; a <= c; a ++)
#define iper(a, b, c) for(int a = b; a < c; a ++)
#define rep(a, b, c) for(int a = b; a >= c; a --)
#define irep(a, b, c) for(int a = b; a > c; a --)
#define aper(A) for(auto i : A) cout << i << ' ';cout << '\n'
#define lowbit(x) ((x) & (-x))
#define debug(x) cout << (x) << endl
#define yes cout << "Yes" << endl
#define no cout << "No" << endl
#define YES cout << "YES" << endl
#define NO cout << "NO" << endl
#define PAI acos(-1)
using ll = long long;
mt19937_64 rnd(chrono::steady_clock::now().time_since_epoch().count());
template<class T> void umin(T &x,T y){if(x>y)x=y;}
template<class T> void umax(T &x,T y){if(x<y)x=y;}
const int mod = 998244353, inf = 1e18;
const double eps = 1e-9;
void add(int &x, int y){x = (x + y) % mod;}
void pre_work(){}

void solve()
{
    int n, m;
    cin >> n >> m;
    vv<int> a(n + 1);
    per(i, 1, n) cin >> a[i];
    vv<int> din(n + 1);
    per(i, 1, m)
    {
        int u, v;
        cin >> u >> v;
        din[u] ++, din[v] ++;
    }
    int ma = 0;
    per(i, 1, n)
        if(din[i] > 1)
            ma = max(ma, a[i]);
    cout << ma << endl;
}	

signed main()
{
#ifdef LOCAL
    freopen("oo.in", "r", stdin);
    freopen("oo.out", "w", stdout);
#endif
 	IOS;
	int tt = 1;
//  	cin >> tt;
	pre_work();
	while(tt --)
	{
		solve();
	}
	return 0;
}

/*
7 7
1 1 2 3 1 2 1
1 2
2 3
1 3
2 4
2 5
5 6
5 7
*/