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
Z = sys.stdin.readline
for t in range(int(Z().strip())):
    n=int(Z().strip())
    l = list(map(int,Z().strip().split()))
    c=1
    m = max(l)
    lst = [x for x in range(n) if l[x]==m]
    for i in lst:
        if i>0 and i<n-1:
            if l[i+1]<l[i] or l[i-1]<l[i]:
                x=i+1
                c=-1
                break
        elif i==0 and l[i+1]<l[i] :
            x=i+1
            c=-1
            break
        elif i==n-1 and l[i-1]<l[i]:
            x=i+1
            c=-1
            break            
            
    print(["-1",(x)][(c<0)])    