402065: GYM100637 K Microcircuits
Memory Limit:256 MB
Time Limit:2 S
Judge Style:Text Compare
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Description
K. Microcircuitstime limit per test2 secondsmemory limit per test256 megabytesinputstandard inputoutputstandard output
You probably know how microcircuits look like. First of all it is important to pay special attention to connections. Contacts on the circuit are connected by lines. If two lines do not intersect then there is no connection between respective contacts.
You are holding a circular circuit with n contacts around the borderline. You have to calculate the number of possibilities to put exactly k non-intersecting lines each connecting two contacts.
InputSingle line contains two integers n and k (1 ≤ k ≤ n ≤ 40).
OutputOutput the required number.
ExamplesInput4 2Output
2Input
4 3Output
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