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 bisect
for _ in range(int(input())):
    n=int(input())
    a=[int(i) for i in input().split()]
    if 1==len(set(a)):
        print('-1')
    else:
        #x=a.index(max(a))
        x=max(a)
        ans=-1
 
        for i in range(n):
           if(a[i]==x):
 
                if(i>0 and a[i-1]!=x):
                    ans=i+1
                if(i<n-1 and a[i+1]!=x): 
                    ans=i+1
 
        print(ans)
    
    