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

cases = int(input())

for _ in range(cases):
    n = int(input())
    ds = list(map(int, input().split()))
    mv = max(ds)
    found = False
    for i, v in enumerate(ds):
        if v == mv:
            if i > 0 and ds[i - 1] < mv:
                print(i + 1)
                found = True
                break
            elif i + 1 < n and ds[i + 1] < mv:
                print(i + 1)
                found = True
                break
    if not found:
        print(-1)
    
    

        
            