Arrangement, generally speaking, m(m≤n) elements are taken from n different elements and arranged in a column in a certain order, which is called the arrangement of taking m elements from n elements. Especially when m=n, this arrangement is called full arrangement, which distinguishes the order of each number. * * * There is one (33,6) = 797448960 species.

Definition of combination:

Taking out any m(m≤n) elements from N different elements and grouping them is called taking out the combination of M elements from N different elements; The number of all combinations of m(m≤n) elements from n different elements is called the number of combinations of m elements from n different elements. Represented by the symbol C(n, m).