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 piranha{
	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];
			int max=0;
			int idx=-1;
			int mc=0;
			for(int i=0;i<n;i++){
				arr[i]=sc.nextInt();
				if(arr[i]>max){
					max=arr[i];
					idx=i;
				}
			}

			int count=0;
			for(int i=0;i<n;i++){
				if(arr[i]==max){
					count++;
				}
			}

			if(count==n){
				System.out.println(-1);
				continue;
			}

			if(count==1){
				System.out.println(idx+1);
				continue;
			}
            int fidx=-1;
			for(int i=1;i<n;i++){
				if(arr[i]<max && arr[i-1]==max){
					fidx =i-1;
					break;
				}
			}
			if(fidx==-1){
				for(int i=0;i<n-1;i++){
					if(arr[i]<max && arr[i+1]==max){
						fidx=i+1;
						break;
					}
				}
			}
			System.out.println(fidx+1);
		}
	}
}