program abc;
uses wincrt;
var  i,j,k:integer;
     stock, price : array [1..4] of real;
     item :array [1..4] of string;
     s : integer;    
begin
  item[1]:='Pen';
  item[2]:='Ruler';
  item[3]:='Pencil';
  item[4]:='Eraser';
  price[1]:=1.50;
  price[2]:=0.8;
  price[3]:=0.5;
  price[4]:=1.2;
  stock[1]:=1000;
  stock[2]:=400;
  stock[3]:=600;
  stock[4]:=200;
  writeln('*** Add Stock ***');
  write('Enter item no.: ');
  readln(s);
  while (s >=5) and (s<=0) do
    begin
      write('Invalid number! Enter item mo. again: ');
      readln(s);
    end;
  case s of
    1:write('How many pens do you added? ');
    2:write('How many rulers do you added? ');
    3:write('How many pencils do you added? ');
    4:write('How many erasers do you added? ');
  end;
  readln(k);
  stock[s] := stock[s]+k;
  writeln('New stock for pen is ',stock[s]:0:0); 
  writeln;
  writeln;
  writeln;
  writeln;
  writeln;
  writeln;
  writeln('*** Buy item ***');
  write('Enter item no.: ');
  readln(s);
  while (s >=5) and (s<=0) do
    begin
      write('Invalid number! Enter item mo. again: ');
      readln(s);
    end;
  case s of
    1:write('How many pens do you buy? ');
    2:write('How many rulers do you buy? ');
    3:write('How many pencils do you buy? ');
    4:write('How many erasers do you buy? ');
  end;
  readln(k);
  if k > stock[s] then
    writeln('Stock is not enough! Please check stock first.')
  else
    begin
      writeln('Item':5,'Price ($)':12,'Quantity':12,'Total ($)':13);
      writeln(item[s]:5,price[s]:12:2,k:12,k*price[s]:13:2);
    end;
end.