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
from collections import defaultdict
input=sys.stdin.readline

for _ in range(int(input())):
    n=int(input())
    lis=list(map(int,input().split()))
    if len(set(lis))==1:
        print(-1)
        continue
    m=max(lis)
    for i in range(n):
        if lis[i]==m:
            if (i>=1 and lis[i-1]<lis[i]) or (i<n-1 and lis[i+1]<lis[i]):
                print(i+1)
                break
