Задача 7 урок 9

http://fkn.ktu10.com/?q=node/8539

Пользователь вводит четыре числа, найдите из них максимальное.

program task7_lesson9;
var
  a,b,c,d:integer;
begin
  writeln('Enter four numbers :');
  readln(a,b,c,d);
  if (a > b) and (a > c) and (a > d) then
     writeln('The biggest number is - a: ',a)
  else begin
      if (b > c) and (b > a) and (b > d) then
      writeln('The biggest number is - b: ',b)
      else
          if (c > a) and (c > b) and (c > d) then
          writeln('The biggest number is - c: ',c)
          else
              if (d > a) and (d > b) and (d > c) then
              writeln('The biggest number is - d: ',d)
 end;
 readln();

end.