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

from sys import stdin,stdout
from collections import Counter
from itertools import permutations
import bisect
import math

I=lambda: map(int,stdin.readline().split())
I1=lambda: stdin.readline()
#(a/b)%m =((a%m)*pow(b,m-2)%m)%m

from sys import stdin,stdout
from collections import Counter
from itertools import permutations
import bisect
import math

I=lambda: map(int,stdin.readline().split())
I1=lambda: stdin.readline()
#(a/b)%m =((a%m)*pow(b,m-2)%m)%m

for _ in range(int(I1())):
    n=int(I1())
    a=list(I())
    ans=-1 
    Max=0
    for i in range(n):
        if (i>0 and a[i]>a[i-1] ) or (i<n-1 and a[i]>a[i+1]):
            if a[i]>=Max:
                ans=i+1 
                Max=a[i]
    print(ans)