comp programming common libraries

Counter.md

to be done

DeQue.md

to be done

Itertools.md

Itertools

Itertools has 4 functions

Permutations

n items from a collection of m

Combinations_With_Replacement

complicated, not often used in comp programming

Combinations

permutations without internal ordering

Product

a, a number of collections, the ways to choose one from each
    one vegetable, one meat, one starch ....
b, one collection, repeated n times, each choosing from the collection
    digits building numbers or letters building words/sentences

Usage

"""
The number of ways to have 3 sorted numbers
between 1 inclusive and X (number of fourth player) exclusive
"""
import itertools
X = int(input())
results = itertools.combinations(range(X - 1), 3)
print(len(results))