7791번 - KBTU party 다국어

문제

At the latest KBTU ”Commencement” party Bakhytzhan noticed that there were n girls D₁,D₂,...,D_n and 2n−1 boys B₁,B₂,...,B_2n−1. And every girl D_j knows exactly boys B₁,B2,...,B2j−1. Throughout the evening party Bakhytzhan tried to count the number of possible choices of exactly r acquainted boys and girls pairs for dancing. That’s why he missed his chance for dancing. Please, write a program that would help Bakhytzhan don’t miss a chance to dance at the next party.

입력

The input file contains two integer numbers n and r (1 ≤ n,r ≤ 10⁶) separated by a space.

출력

Output file should contain answer to Bakhytzhan’s problem – residue modulo 2946859

제한

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