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

from collections import defaultdict
def solve(n,a):
    p = -1 
    for i in range(n):
        if i > 0 and a[i-1] < a[i]:
            p = i+1
            break
    for i in range(n):
        if i < n-1 and a[i+1] < a[i]:
            p = i+1
            break
        #print(p)
    
    return p
    
t = int(input())
while t:
    n = int(input())
    a = list(map(int,input().split()))
    print(solve(n,a))
    t-=1 
    
