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