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

import math
import sys

# 113759
input = lambda: sys.stdin.readline().rstrip()
for _ in range(int(input())):
    n = int(input())
    a = list(map(int, input().split()))
    c = max(a)
    ans = -1
    for i in range(n):
        if i == 0:
            if a[i] == c and a[i] > a[i + 1]:
                ans = i + 1
                break
        elif i == n - 1:
            if a[i] == c and a[i] > a[i - 1]:
                ans = i +1
                break
        else:
            if a[i] == c and (a[i] > a[i+1] or a[i] >a[i -1]):
                ans = i +1
                break
    print(ans)
