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

def ans(a,n):
        x=max(a)
        
        if a[0]==x and a[0]>a[1]:
                return 1
        for i in range(1,n-1):
                if a[i]==x:
                        if a[i]>a[i+1] or a[i]>a[i-1]:
                                return i+1
        if a[n-1]>a[n-2]:
                return n
        return -1
        
for _ in range(int(input())):
        n=int(input())
        c=0
        x=[]
        l=list(map(int,input().split()))
        res=ans(l,n)
        print(res)
                
                
                
