var a,b,c,t:integer;beginreadln(a,b,c);if (a+b>c) and (b+c>a) and (c+a>b) then
begin
if a<b then begin t:=a;a:=b;b:=t; end;
if a<c then begin t:=a;a:=c;c:=t; end;
if b*b+c*c=a*a then writeln(b*c/2:0:1)
else writeln('No');
end
else write('No') ;end....
