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 class Answer {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int t = sc.nextInt();
		while(t-->0){
			int n = sc.nextInt();
			int[] arr = new int[n];
			for(int i = 0; i<n; i++) arr[i]=sc.nextInt();
			
			boolean allsame = true;
			for(int i = 1; i<n; i++){
				if(arr[i]!=arr[i-1]){
					allsame=false;
					break;
				}
			}

			if(!allsame){
				int[] copt = arr.clone(); Arrays.sort(copt); int big = copt[n-1];
				for(int i = 0; i<n; i++){
					if(arr[i]==big){
						System.out.println(i+1); break;
					}
				}
			}else{
				System.out.println(-1);
			}
			
		}
		
	}
}