program z3_33;
var a,b,c :integer;
s,p:real;
begin
write('vvedite dliny storon treugolnika a ,b c ');
read(a, b,c);
p:=(a+b+c)/2;
s:=sqrt(p*(p-a)*(p-b)*(p-c));
write('S=',s);
readln;
end.