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

import math 
t= int(input())
for i in range(t): 
    n = int(input())
    l = list(map(int,input().split()))
    a = max(l)
    if len(set(l))==1:
        print(-1)
    elif l[0]==a and l[1]!=a:
        print(1)
    elif l[-1]==a and l[-2]!=a:
        print(n)
    else:
        ans=-1
        for j in range(1,n-1):
            if l[j]==a and (l[j-1]!=a or l[j+1]!=a):
                
                ans=(j+1)
                break
        print(ans)