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):
    x = max(a)
    for i in range(n):
        if a[i] == x and ((i!= 0 and a[i-1] != x) or (i!= n-1 and a[i+1]!=x)):
            return i+1 
    return -1
        
        
    
t = int(input())
while t:
    n = int(input())
    a = list(map(int,input().split()))
    print(solve(n,a))
    t-=1 
    