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

for _ in range(int(input())):
    input()
    x = list(map(int,input().split()))
    l = max(x)
    ans = -1
    for i in range(len(x)):
        if x[i]==l and (x[max(i-1,0)]<x[i] or x[min(i+1,len(x)-1)]<x[i]):
            ans = i
    if ans!=-1:
    	print(ans+1)
    else:
    	print(ans)
        
