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

t = int(sys.stdin.readline())

for _ in range(t):
    n = int(sys.stdin.readline())
    lst = list(map(int, sys.stdin.readline().split()))

    maxs = max(lst)
    ans = -1
    for i in range(n):
        if lst[i] == maxs:
            if i == 0 and lst[i+1] < maxs:
                ans = i+1
                break
            elif i == n-1 and lst[i-1] < maxs:
                ans = i+1
                break
            elif (0 < i < n-1) and  (lst[i-1] < maxs or lst[i+1] < maxs):
                ans = i+1
                break
    
    print(ans)