program z2;
uses crt;
var a, b,c,p, s: real;
begin
textbackground(yellow); textcolor(blue);
clrscr;
gotoxy(25,15);
write('a=');
readln(a);
gotoxy(25,16);
write('b=');
readln(b);
gotoxy(25,17);
write('c=');
readln(c);
p:=(a+b+c)/2;
gotoxy(25,20);
s:=sqrt(p*(p-a)*(p-b)*(p-c));
writeln('s=',s);
readkey;
end.4