SmallestMovedPointPerm( perm )
SmallestMovedPointPerm returns the smallest point moved by the
permutation perm, i.e., the smallest positive integer i such that
i^perm < i. It will signal an error if perm is trivial
(see also LargestMovedPointPerm).
gap> SmallestMovedPointPerm( (4,7,5) );
4
GAP 3.4.4