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())
for i in range(t):
    n = int(input())
    l = list(map(int,input().split()))
    m = max(l)
    for j in range(n):
        if l[j] == m:
            b1 = False
            b2 = False
            if j >= 1:
                if l[j-1] != m:
                    b1 = True
            if j < n-1:
                if l[j+1] != m:
                    b2 = True
            if b1 or b2:
                print(j+1)
                break
            
    else:
        print(-1)
    
