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

# cook your dish here
def solve():
    n = int(input())
    lst = list(map(int, input().split()))
    
    maxx = -1
    indx = -1
    
    for i in range(n):
        if i==0:
            if lst[i] > lst[i+1]:
                maxx = lst[i]
                indx = i
        elif i==n-1:
            if lst[i] > lst[i-1] and lst[i] > maxx:
                maxx = lst[i]
                indx = i
        else:
            if lst[i] > maxx:
                if lst[i] > lst[i-1] or lst[i] > lst[i+1]:
                    maxx = lst[i]
                    indx = i
    
    if indx !=-1:
        indx+=1
    print(indx)
    
        
        
        
    
    
    
    
    
    return

if __name__ == "__main__": 
    t = int(input())
    while t!=0:
        solve()
        t-=1
    
