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

import math
for _ in range(int(input())):
    n=int(input())
    a=list(map(int,input().split()))
    x=max(a)
    if a.count(x)==n:
        print(-1)
    else:
        p=a.index(x)
        if (p==0 and a[1]==x):
            for i in range(p+1,n):
                if a[i+1]<x:
                    p=i
                    break
        print(p+1)