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