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

t = int(input())
 
ll = []
 
for _ in range(t):
    _ = input()
    ss = input().split()
    ll.append([int(s) for s in ss])
 
for l in ll:
    m = max(l)
    isEqual = True
    for e in l:
        if e != m:
            isEqual = False
            break
    if isEqual:
        print(-1)
    else:
        for i in range(len(l)):
            if l[i] == m and ((i<len(l)-1 and l[i+1] != m) or (i>0 and l[0] != m)):
                print(i+1)        
                break
