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())
    arr = list(map(int, input().split()))
    check = False
    m = max(arr)
    for i in range(n):
        if i == 0 and arr[0] == m:
            if arr[i+1] < m:
                print(i+1)
                check =True
                break
        elif i == n-1 and arr[-1] == m:
            if arr[i-1] < m:
                print(i+1)
                check = True
                break
        else:
            if arr[i] == m:
                if arr[i-1] < m:
                    print(i+1)
                    check = True
                    break
                elif arr[i+1] < m:
                    print(i+1)
                    check = True
                    break
                else:
                    continue
        
    if check == False:
        print(-1)
    