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 re

def readGenerator():
    while True:
        tokens = input().split(' ')
        for t in tokens:
            yield t

reader = readGenerator()

def readWord():
    return next(reader)

def readInt():
    return int(next(reader))

def readFloat():
    return float(next(reader))

def readLine():
    return input()

def solve(a, n):
    m = max(a)
    for i in range(0, n):
        if a[i] == m and ((i > 0 and a[i - 1] != m) or (i < n - 1 and a[i + 1] != m)):
            return i + 1

    return -1

t = readInt()
for _ in range(t):
    n = readInt()
    a = [readInt() for _ in range(n)]
    print(solve(a, n))