var h,dx,x,result:real;
function visl(h,dx,x:real):real;
  begin
  visl:=h/3*(sqr(dx)*sqr(cos(x+3*dx/sqr(h))))-dx*sqr(cos(x+dx/h))-sqr(dx)*sqr(cos(x+2*dx/sqr(h)));
  end;
begin
 x:=2.5094;
 dx:=x/19;
 h:=x/8;
 result:=visl(h,dx,x);
 writeln(result:2:10);
 readln;
end.