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

#
# Created by Polusummator on 24.10.2020
# --------- Little PyPy Squad ---------
# Verdict: 
#
t = int(input())
for _ in range(t):
    n = int(input())
    a = [int(i) for i in input().split()]
    m = max(a)
    ans = -1
    for i in range(n):
        z = False
        if a[i] == m:
            if i == 0:
                if a[i] > a[i + 1]:
                    z = True
            elif i == n - 1:
                if a[i - 1] < a[i]:
                    z = True
            else:
                if a[i - 1] < a[i] or a[i] > a[i + 1]:
                    z = True
            if z:
                ans = i + 1
                break
    print(ans)
