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())
for _ in range(t):
    
    n = int(input())
    a = list(map(int, input().split()))
    mx = max(a)
    idx = -1
    for i in range(n):
        if a[i] != mx:
            continue
        if i > 0 and a[i-1] != mx:
            idx = i + 1
        if i < n-1 and a[i+1] != mx:
            idx = i + 1
    print(idx)