fact: Definition row_perm (s : 'S_m) A := \matrix[row_perm_key]_(i, j) A (s i) j.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype finfun bigop finset fingroup perm order) mathcomp(div prime binomial ssralg countalg finalg zmodp)