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

#define pb push_back
#define F first
#define S second


vector<int>node[100005];
int dsu[100005],a[100005];
int num=0;
int n,m;
int p1[100005],p2[100005],kuai[100005];

void init(){
    for(int i=1;i<=n;i++) dsu[i]=i;
    num=0;
}

int find(int g){
    if(g==dsu[g]) return g;
    dsu[g]=find(dsu[g]);
    return dsu[g];
}

void un(int g,int h){
    g=find(g),h=find(h);
    // cerr<<g<<" "<<h<<"\n";
    if(g==h) return;
    dsu[g]=h;
    num--;
}

int main(){
    ios::sync_with_stdio(0);
    cin.tie(0);
    cin>>n>>m;
    init();

    vector<int>all;
    vector<pair<int,int>>gogo;
    for(int i=1;i<=n;i++){
        int g;
        cin>>g;
        a[i]=g;
        gogo.pb({g,i});
        all.pb(g);
    }

    sort(all.begin(),all.end());
    sort(gogo.begin(),gogo.end());
    all.resize(distance(all.begin(),unique(all.begin(),all.end())));

    for(int i=1;i<=m;i++){
        int g,h;
        cin>>g>>h;
        node[g].pb(h);
        node[h].pb(g);
    }
    if(all.size()==1){
        cout<<"-1\n";
        return 0;
    }

    int id=0;int now=0;
    for(int i=0;i<all.size();i++){
        int ii=all[i];
        while(id<gogo.size()&&gogo[id].F<=ii){
            num++;
            now++;
            for(int mm:node[gogo[id].S]){
                if(a[mm]<=ii){
                    // cerr<<all[i]<<" "<<mm<<" "<<gogo[id].S<<"\n";
                    un(mm,gogo[id].S);
                }
            }
            id++;
        }
        p1[i]=now;p2[i]=n-now;
        kuai[i]=num;
    }

    init();id=gogo.size()-1;
    for(int i=all.size()-2;i>=0;i--){
        int ii=all[i];
        while(id>=0&&gogo[id].F>ii){
            num++;
            for(int mm:node[gogo[id].S]){
                if(a[mm]>ii){
                    un(mm,gogo[id].S);
                }
            }
            id--;
        }
        kuai[i]+=num;
        // cerr<<num<<" "<<i<<"\n";
    }


    for(int i=0;i<all.size();i++){
        // cerr<<p1[i]<<" "<<p2[i]<<" "<<kuai[i]<<"\n";
        if(p1[i]>=kuai[i]-1&&p2[i]>=kuai[i]-1){
            cout<<all[i]<<"\n";
            return 0;
        }
    }

    cout<<"-1\n";
}