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.io.*;

public class C {

	public static void main(String[] args) throws Exception{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		int t = Integer.parseInt(br.readLine());
		while(t-- > 0) {
			int n = Integer.parseInt(br.readLine());
			String[] in = br.readLine().split(" ");
			int[] arr = new int[n];
			for (int i = 0; i < arr.length; i++) {
				arr[i] = Integer.parseInt(in[i]);
			}
			
			int mx = Integer.MIN_VALUE;
			for (int i = 0; i < arr.length; i++) {
				if (arr[i] > mx) {
					mx = arr[i];
				}
			}
			
			int idx = -1;
			for (int i = 0; i < n; ++i) {
				if (arr[i] != mx) continue;
				if (i > 0 && arr[i - 1] != mx) idx = i + 1;
				if (i < n - 1 && arr[i + 1] != mx) idx = i + 1;
			}
			
			System.out.println(idx);
		}
	}

}
