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 u in range(int(input())):
    n = int(input())
    x = [int(w) for w in input().split()]
    
    if(len(set(x)) == 1):
        print(-1)
        
    else:
        print(1 + x.index(max(x)))