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

import collections
for t in range(int(input())):
    n=int(input())
    nums=list(map(int,input().split()))
    if len(set(nums))==1:
        print(-1)
        continue
    val=max(nums)
    out=0
    for i in range(n):
        if nums[i]==val:
            if i>0 and nums[i-1]<val:
                out=i
                break
            if i<n-1 and nums[i+1]<val:
                out=i
                break
    print(out+1)