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

for _ in range(int(input())):
    n = int(input())
    l = list(map(int,input().split()))
    mIn,mAx = min(l),max(l)
    if mIn==mAx:
        print(-1)
        continue
    for i in range(n):
        if l[i]==mAx:
            if (i>0 and l[i-1]!=mAx) or (i<n-1 and l[i+1]!=mAx):
                print(i+1)
                break