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 = list(map(int, input().split()))
    if len(set(a)) == 1:
        print(-1)
    else:
        mx = max(a)
        ind = -1
        if a[0] == mx and a[0] > a[1]:
            ind = 1
            
        if a[-1] == mx and a[-1] > a[-2]:
            ind = n
            
        for i in range(1,n-1):
            if a[i] > a[i-1] or a[i] > a[i+1]:
                if a[i] == mx:
                    ind = i+1
                    
        print(ind)