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

t = int(input())

def dominant(piranhas, n):
    m = max(piranhas)
    for j in range(n):
        if piranhas[j] == m:
            if j-1 >= 0 and piranhas[j-1] < m:
                return j+1
            if j+1 < n and piranhas[j+1] < m:
                return j+1
    return -1

for i in range(t):
    n = int(input())
    piranhas = list(map(int, input().split()))
    print(dominant(piranhas, n))