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):
    k = int(input())
    a = list(map(int,input().split()))
    if len(set(a)) == 1:
        print(-1)
        continue
    high = -99999
    ind = -1
    for i in range(len(a)):
        if a[i]>high:
            high = a[i]
            ind = i
    if high == -99999:
        print(-1)
    else:
        print(ind+1)