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())
    s = list(map(int,input().split()))
    
    m = -1
    v = -1
    for i in range(n):
        if s[i]>v and (s[i]>s[max(0,i-1)] or s[i]>s[min(n-1,i+1)]):
            m = i
            v = s[i]
    if(m==-1):
        print(-1)
    else:
        print(m+1)
