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 t in range(int(input())):
    n = int(input())
    a = list(map(int,input().split()))
    ans = 0
    dom = max(a)
    ind = []
    for i in range(n):
        if a[i] == dom:
            ind.append(i)
    loc = -1
    for x in ind:
        if x == 0:
            if a[1] < a[x]:
                loc = x + 1
                break
        elif x == (n-1):
            if a[n-2] < a[x]:
                loc = x + 1
                break
        else:
            if a[x-1] < a[x] or a[x + 1] < a[x]:
                loc = x + 1
    print(loc)
    
    
    
