Distributing the balls by llhuii(mitchs (Rivu Das))

f=lambda n,k:n+k<1or(n>=k and f(n-1,k-1)+f(n-1,k))*k
while 1:print f(*map(int,raw_input().split()))

Note that non-ascii characters in the above source code will be escaped (such as \x9f).

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