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 math
t = int(input())
for _ in range(t):
    
    n = int(input())
    l = [int(x) for x in input().split()]
    a = max(l)
    if(l[0] == a):
        flag = 1
        for i in range(n):
            if l[i] != a:
                print(i)
                flag = 0
                break

        if(flag ==1):
            print(-1)

    else:
        flag = 1
        for i in range(n):
            if l[i] == a:
                print(i+1)
                flag = 0
                break

        if(flag == 1):
            print(-1)

