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 q in range(t):
    n = int(input())
    a = list(map(int, input().split()))
    b = max(a)
    for i in range(n):
        if a[i] == b:
            if i == 0:
                if a[1] != a[0]:
                    print(1)
                    break
            elif i == n-1:
                if a[n-2] != a[n-1]:
                    print(n)
                    break
            else:
                if a[i] != a[i-1] or a[i] != a[i+1]:
                    print(i+1)
                    break
    else:
        print(-1)
