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



for i in range(int(input())):
    n = int(input())
    s = list(map(int, input().split()))
    # fir = s[0]
    m = max(s)
    f = 0
    r = 0
    x = 0
    if s[0]==m and  s[1]<m:
        print(1)
    elif (s[len(s)-1]==m and s[len(s)-2]!=m):
        print(len(s))
    else:
        for j in range(1,len(s)-1):
            if s[j]==m and (s[j-1]!=m or s[j+1]!=m):
                print(j+1)
                break
        else:
            print(-1)


