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()))
    ans = -1
    if max(a) == min(a):
        print(-1)
        continue
    else:
        M = max(a)
        for i in range(n):
            if a[i] == M:
                if i > 0:
                    if a[i-1] != M:
                        ans = i+1
                        break
                if i < n-1:
                    if a[i+1] != M:
                        ans = i+1
                        break
        print(ans)
