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.Scanner;

public class C {

	public static void main(String[] args) {
		Scanner input = new Scanner(System.in);
		int t = input.nextInt();
		while(t-->0) {
			int n = input.nextInt();
			int[] a = new int[n];
			for(int i=0; i<n; i++) {
				a[i] = input.nextInt();
			}
			int max = -1;
			for(int i=0; i<n; i++) {
				if(max<a[i]) {
					max = a[i];
				}
			}
			int ans = -1;
			for(int i=0; i<n; i++) {
				if(a[i]==max) {
					if(i==0) {
						if(a[0]>a[1]) {
							ans = 1;
							break;
						}
					}
					else if(i==n-1) {
						if(a[n-1]>a[n-2]) {
							ans = n;
							break;
						}
					}
					else {
						if(a[i]>a[i-1]||a[i]>a[i+1]) {
							ans = i+1;
							break;
						}
					}
				}
			}
			System.out.println(ans);
		}
		input.close();
		
	}

}
