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())
while t > 0:
    t -= 1
    ans = 0
    n = int(input())
    l = list(map(int,input().split(' ')))
    maxs = max(l)
    if(l[0]==maxs and l[1] < maxs):
        print(1)
        continue
    elif(l[n-1]==maxs and l[n-2] < maxs):
        print(n)
        continue
    else:
        for i in range(1,n-1):
            if(l[i]==maxs and (l[i-1] < maxs or l[i+1] < maxs)):
                print(i+1)
                ans = 1
                break
        if(ans==0):
            print(-1)