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 sys

# t = map(int, input().split())
t = int(input())
while t > 0:
    t -= 1
    n = int(input())
    arr = list(map(int, input().split()))
    maxi = max(arr)

    dominatingPiranha = -1
    for i in range(n):
        if i == 0 and arr[i] == maxi:
            if arr[i + 1] < maxi:
                dominatingPiranha = i + 1
        elif i == n - 1 and arr[i] == maxi:
            if arr[i - 1] < maxi:
                dominatingPiranha = i + 1
        elif arr[i] == maxi:
            if arr[i - 1] < maxi or arr[i + 1] < maxi:
                dominatingPiranha = i + 1
    print(dominatingPiranha)
