ZOJ Problem Set - 3662
Yesterday, my teacher taught us about math: +, -, *, /, GCD, LCM... As you know, LCM (Least common multiple) of two positive numbers can be solved easily because of a * b = GCD (a, b) * LCM (a, b).
In class, I raised a new idea: "how to calculate the LCM of K numbers". It's also an easy problem indeed, which only cost me 1 minute to solve it. I raised my hand and told teacher about my outstanding algorithm. Teacher just smiled and smiled...
After class, my teacher gave me a new problem and he wanted me solve it in 1 minute, too. If we know three parameters N, M, K, and two equations:
1. SUM (A1, A2, ..., Ai, Ai+1,..., AK) = N
Can you calculate how many kinds of solutions are there for Ai (Ai are all positive numbers). I began to roll cold sweat but teacher just smiled and smiled.
Can you solve this problem in 1 minute?
There are multiple test cases.
Each test case contains three integers N, M, K. (1 ≤ N, M ≤ 1,000, 1 ≤ K ≤ 100)
For each test case, output an integer indicating the number of solution modulo 1,000,000,007(1e9 + 7).
You can get more details in the sample and hint below.
4 2 2 3 2 2
The first test case: the only solution is (2, 2).
The second test case: the solution are (1, 2) and (2, 1).
Contest: The 2012 ACM-ICPC Asia Changchun Regional Contest