1
3
5 3 4
 6
5
5 3 4 4 5
3
1 1 1
5
4 4 3 4 4
5
5 5 4 3 2
3
1 1 2
5
5 4 3 5 5
 1
3
10 1 5

1
 1
-1
2
2
3
1
 1


import java.util.*;

public final class Q3 {
	public static void main (String[] args) {
		Scanner sc = new Scanner(System.in);
		int t  = sc.nextInt();
		while(t-- > 0){
		    int n = sc.nextInt();
		    int[]a = new int[n];
		    for(int i=0 ; i<n ; i++){
		        a[i] = sc.nextInt();
		    }
		    boolean as = true;
		    int max = a[0];
		    int index = 0;
		    for(int i=1 ; i<n ; i++){
		        if(as){
		            if(a[i] != a[i-1])
		              as = false;
		        }
		         if(a[i] >= max && (a[i] > a[i-1]) )
		            index = i+1;
		         else if(i != n-1){
		          if(a[i] >= max && (a[i] > a[i+1]) )
		            index = i+1;   
		         }
		           max = Math.max(max , a[i]);
		    }
		    int ans;
		    if(as)
		      ans = -1;
		    else 
		      ans = index;
		    System.out.println(ans);
		      
		}
	}
}