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 sys
import math
from collections import defaultdict,deque

input = sys.stdin.readline
def inar():
    return [int(el) for el in input().split()]
def main():
    t=int(input())
    for _ in range(t):
        n=int(input())
        arr=inar()
        take=max(arr)
        ans=-1
        for i in range(n):
            lol=0
            if arr[i]==take:

                if (i-1)>=0 and arr[i-1]<arr[i]:
                    lol=1

                if (i+1)<n and arr[i+1]<arr[i]:
                    lol=1

            if lol:
                ans=i+1
                break
        print(ans)




if __name__ == '__main__':
    main()



