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 tt  in range(int(input())):
    n=int(input())
    l=list(map(int,input().split()))
    mx=max(l);ans=-1
    for i in range(n):
        if l[i]==mx:
            if i-1>=0 and l[i-1] < mx:
                ans=i+1
            elif i+1<n and l[i+1] < mx:
                ans=i+1
    print(ans)
                
        
