1.2 Rectangle area

program Rectagnle;
var
x1 : real;
y1 : real;
x2 : real;
y2 : real;
sum : real;
begin
    writeln('Enter x1: ');
    readln(x1);
    writeln('Enter y1: ');
    readln(y1);
    writeln('Enter x2: ');
    readln(x2);
    writeln('Enter y2: ');
    readln(y2);
    sum:=(x2-x1)*(y2-y1);
    writeln('The sum is: ');
    writeln(sum);
end.