#include<bits/stdc++.h>
using namespace std;
#define int long long
#define INF 0x3f3f3f3f3f3f3f3f
#define pii pair<int,int>
#define fi first
#define se second
#define all(_a) _a.begin(), _a.end()
const int N= 1000010;
int primes[N], cnt,minp[N];
bool st[N];


void solve(){
    int n,m;
    cin>>n>>m;
    vector<int> d(n+1),a(n+1);
    for(int i=1;i<=n;i++) cin>>a[i];
    for(int i=1;i<=n;i++){
        int u,v;
        cin>>u>>v;
        d[u]++;
        d[v]++;
    }
    if(n==1){
        cout<<a[1]<<endl;
        return;
    }
    int res=0;
    for(int i=1;i<=n;i++){
        if(d[i]>1) res=max(res,a[i]);
    }
    sort(all(a));
    res=max(res,a[n-1]);
    cout<<res<<endl;

}
signed main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr), cout.tie(nullptr);
    cout << setiosflags(ios::fixed) << setprecision(15);
    int T;
    T=1;
    
    
    //cin>>T;
    while(T--)solve();
    return 0;
}