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

#!/usr/bin/env python
# coding: utf-8

# In[5]:


def solve(n, arr):
    res = max(arr)
    for i in range(n):
        if arr[i] == res:
            if arr[i] > arr[max(i-1, 0)] or arr[i] > arr[min(i+1, n-1)]:
                return i+1
    return -1
    
if __name__ == '__main__':
    t = int(input())
    for i in range(t):
        n = int(input())
        arr = [int(i) for i in input().split()]
        print(solve(n, arr))


# In[ ]:




