Permutations can also be written in cycle notation.
A cycle of a permutation consists of an element and its images we obtain
by successively applying of this permutation until the starting element is
reached again. By means of the elements not occurring in the first cycle
further cycles are constructed until each element occurs in (exactly) one of
the cycles found by the above construction. The cycles of a permutation
are written down in parentheses one after another in descending order by the
number of elements occurring in the cycle. Cycles of length 1 are usually
omitted.