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

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