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

t = int(input())
for _ in range(t):
    n = int(input())
    a = list(map(int, input().split()))
    b = max(a)
    if a[0] == b and a[0] > a[1]:
        print(1)
    elif a[n-1] == b and a[n-1] > a[n-2]:
        print(n)
    else:
        ans = -1
        for i in range(1, n-1):
            if a[i] == b:
                if a[i] > a[i+1] or a[i] > a[i-1]:
                    ans = i+1
                    break
        print(ans)
            
            
        
    
        
                
        
                
            
    
    
    
    
        
        
        
        
    
        
        
        
    
        
                
    
        
        
            
        
        
    
    
    
            
        
    
            
        
    
        
    
            
        
    
    
        
            
    
    
        
    
        
            
            
            
        
            
            
            
            
            
            

    
        
        
        
        
    
    
        
            
    
        
        
                
            
            
            
            
    
            
                
        
        
    
            
    
        
            
        
    

    
    
    
           
        
        
        
            

        
    
        
    
    
    
