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

test_cases=int(input())
for test_case in range(test_cases):
    n=int(input())
    a = list(map(int,input().split()))
    mx=max(a)
    ans=-1
    for i in range(n):
        if i!=0 and i!=n-1:
            if a[i]==mx:
                if a[i-1]<a[i] or a[i+1]<a[i]:
                    ans=i+1
                    break
        elif i==0:
            if a[0]==mx:
                if a[1]<a[0]:
                    ans=1
                    break
        elif i==n-1:

            if a[-1]==mx:
                
                if a[-1]>a[-2]:
                    ans=n
                    break

    print(ans)