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 sys

def main():
    n = int(input())
    q = list(map(int, input().split()))
    print(1 + q.index(max(q)) if len(set(q)) != 1 else -1)
for i in range(int(input())):
    main()