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 t in range(int(input())):
    ip=int(input())
    lsip=list(map(int,input().split()))
    maxval=max(lsip)
    cmax=lsip.count(maxval)
    if cmax==ip:
        print(-1)
    elif cmax==1:
        print(lsip.index(maxval)+1)
    else:
        for i in range(ip):
            if lsip[i]==maxval:
                if i-1>=0 and lsip[i-1]<maxval:
                    print(i+1)
                    break
                elif i+1<ip and lsip[i+1]<maxval:
                    print(i+1)
                    break

        