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)
    
    for i in range(n):
        if l[i]!=m:
            continue
        if i>0 and l[i-1]!=m:
            c=i+1
            break
        if i<n-1 and l[i+1]!=m:
            c=i+1
            break
            
    print(c)    