DSU

/*
    Task        : Disjoint Set Union [DSU]
    Author      : Phumipat C. [MAGCARI]
    Language    : C++
*/
#include<bits/stdc++.h>
using namespace std;
int p[100010],sol[100010];
int findroot(int now){
    if(p[now] == now)
        return now;
    else
        return p[now] = findroot(p[now]);
}
int main(){
    int n,m,u,v,ru,rv;
    scanf("%d %d",&n,&m);
    for(int i=1;i<=n;i++){
        scanf("%d",&sol[i]);
        p[i] = i;
    }
    while(m--){
        scanf("%d %d",&u,&v);

        ru = findroot(u);
        rv = findroot(v);

        if(ru == rv){
            printf("-1\n");
        }else{
            if(sol[ru]>sol[rv] || (sol[ru] == sol[rv] && ru<rv)){
                printf("%d\n",ru);
                sol[ru]+=sol[rv]/2;
                p[rv] = ru;
            }else if(sol[rv]>sol[ru] || (sol[ru] == sol[rv] && rv<ru)){
                printf("%d\n",rv);
                sol[rv]+=sol[ru]/2;
                p[ru] = rv;
            }
        }
    }
    return 0;
}