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
# input = lambda: sys.stdin.readline().rstrip()
input = sys.stdin.buffer.readline 


for _ in range(int(input())):
    n=int(input())
    a=[int(i) for i in input().split()]
    maxx=max(a); ans=-1
    for i in range(n):
        if a[i]==maxx and ((i+1<n and a[i+1]<maxx) or (i-1>=0 and a[i-1]<maxx)):
            ans=i+1
            break
    print(ans)