# your code goes here
def binomial(n,k):
    if n < 0 or k < 0 or k > n: return 0
    b = 1
    for i in range(k): b = b*(n-i)//(i+1)
    return b
 
def unchoose(n,S):
    k = len(S)
    if k == 0 or k == n: return 0
    j = S[0]
    if k == 1: return j
    S = [x-1 for x in S]
    if not j: return unchoose(n-1,S[1:])
    return binomial(n-1,k-1)+unchoose(n-1,S)
 
def choose(X,k):
    n = len(X)
    if k < 0 or k > n: return []
    if not k: return [[]]
    if k == n: return [X]
    return [X[:1] + S for S in choose(X[1:],k-1)] + choose(X[1:],k)
 
(n,k) = (7,3)
for S in choose(list(range(n)),k): print((unchoose(n,S),S))

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