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

from collections import deque
t=int(input())
for i in range(t):
    n=int(input())
    l=list(map(int,input().split()))
    t=max(l)
    flag=True
    for i in range(n):
        if l[i]==t:
            if i==0:
                if l[i]>l[i+1]:
                    print(1)
                    flag=False
                    break
            elif i==n-1:
                if l[i]>l[i-1]:
                    print(n)
                    flag=False
                    break
            else:
                if l[i]>l[i+1] or l[i]>l[i-1]:
                    print(i+1)
                    flag=False
                    break
    if flag:
        print(-1)
                    
                
        
        
        
        