program t41;
var
  a : string [20];
  b : string [20];
  c : string [4];

begin
  a := 'hello';
  writeln (a);
  b := 'world';
  a := b;
  writeln (a);
  c := a;
  writeln (c);
  a := c;
  writeln (a);
  b := '';
  a := b;
  writeln (a);
  writeln ('end')
end.