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 _ in range(t):
    n = int(input())
    
    a = [*map(int, input().split(' '))]
    
    m = max(a)
    
    index = -1
    for i in range(len(a)):
        if a[i]==m:
            if (i>0 and a[i-1]<m) or (i<len(a)-1 and a[i+1]<m):
                index = i+1
                break

    print(index)
