BZOJ2729 [HNOI2012]排队

 1 /**************************************************************
 2     Problem: 2729
 3     User: rausen
 4     Language: Python
 5     Result: Accepted
 6     Time:708 ms
 7     Memory:8736 kb
 8 ****************************************************************/
 9  
10 n, m = [int(st) for st in raw_input().split()]
11 fac = [1] * 2010
12 for i in range(1, 2010) : fac[i] = fac[i - 1] * i
13 def c(n, m) :
14     if (n < m): return 0
15     return fac[n] / fac[n - m]
16 print c(n, n) * (c(n + 1, 2) * c(n + 3, m) + 2 * (n + 1) * c(n + 2, m - 1) * m)