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

void solve()
{
    int n,m;
    cin>>n>>m;
    vector<int>ar(n + 1),du(n + 1);
    for(int i = 1;i <= n;i ++)
        cin>>ar[i];
    for(int i = 1;i <= m;i ++){
        int u,v;
        cin>>u>>v;
        du[u] ++,du[v] ++;
    }
    if(n == 1){
        cout<<ar[1]<<"\n";
        return;
    }
    int mx = 0;
    for(int i = 1;i <= n;i ++)
        if(du[i] >= 2)
            mx = max(mx,ar[i]);
    cout<<mx<<"\n";
}

signed main()
{
    ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
    // int T;
    // cin>>T;
    // while(T --)
        solve();
}