var s,p,a,b,c : real;
begin
writeln('a = ');
readln(a);
writeln('b = ');
readln(b);
writeln('c = ');
readln(c);
p = (a+b+c)/2;
s = sqrt(p*(p-a)*(p-b)*(p-c));
writeln('s = ',s);
end.
var s,p,a,b,c : real;
begin
writeln('a = ');
readln(a);
writeln('b = ');
readln(b);
writeln('c = ');
readln(c);
p = (a+b+c)/2;
s = sqrt(p*(p-a)*(p-b)*(p-c));
writeln('s = ',s);
end.