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

a = input()
for x in range(int(a)):
    b = input()
    c = input().split(" ")
    d = [int(i) for i in c]
    tag = max(d)
    ans = -1
    for i in range(len(d)):
        if(i==0):
            if(d[i]==tag and d[i+1]<tag):
                ans = i+1
                break
        elif(i==len(d)-1):
            if(d[i]==tag and d[i-1]<tag):
                ans = i+1
                break
        else:
            if(d[i]==tag and (d[i+1]<tag or d[i-1]<tag)):
                ans = i+1
                break
    print(ans)

