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 sys
input=sys.stdin.readline
T=int(input())
for _ in range(T):
    n=int(input())
    A=list(map(int,input().split()))
    v=max(A)
    flag=0
    for i in range(n):
        if (A[i]!=v):
            flag=1
            break
    if (flag==1):
        ans=n
        for i in range(n-1):
            if (A[i]==v and A[i+1]!=v):
                ans=i+1
                break
        for i in range(n-1,0,-1):
            if (A[i]==v and A[i-1]!=v):
                ans=i+1
                break
        print(ans)
    else:
        print(-1)
