Labor Day is coming. Boss Niu has prepared $n$ identical gifts for his staff generously, and all of the gifts will be given away. It is known that in Boss Niu's company, there are $m$ staff in total. Due to limited gifts, each of the staff can get at least one gift, and at most $k$ gifts.
Now Boss Niu wonders how many different ways can he distribute his gifts. Two ways are considered different if exists one staff at least, who gets $x$ gifts in the first way and gets $y$ gifts in the second way($x\neq y$). Please note that all the gifts are considered same.
Since the answer may be large, you only need to output it modulo $100000007$.