begin
  'abc'.Permutations.Println;
  'abc'.Permutations(2).Println;
  'abc'.Combinations(2).Println;
  'abc'.CartesianPower(2).Println;
  //Arr('a','b','c').CartesianPower(2).PrintLn;
  'abc'.Cartesian('def').Println;
end.