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

def solution():
    n=int(input())
    arr=list(map(int,input().split()))
    ans=-1
    MAX=max(arr)
    for i in range(n):
        if arr[i]==MAX:
            if i-1>-1:
                if arr[i-1]<MAX:
                    return i+1
            if i+1<n:
                if arr[i+1]<MAX:
                    return i+1
    return ans
def main():
    T=int(input())
    for t in range(1,T+1):
        print(solution())
if __name__ == "__main__":
    main()