#include <stdio.h>
#include <iostream>
#include <string.h>
#include <math.h>
using namespace std;
double f(double x)
{
  return (x*x*x-3*x*x+3*x-1);
}
double erfen(double x1,double x2,double (*p)(double))//double (*p)(double)为形参，相当于函数别名
{
  double xx;
  do
  {
    xx=(x1+x2)/2;
    if((*p)(xx)*(*p)(x1)>0)
      x1=xx;
    else
      x2=xx;
  }while(fabs((*p)(xx))>=1e-7);//le-7代表1*10的-6次方，它的值将影响到跟的准确度的问题
  return xx;
}
int main()
{
  double x1,x2;
  double f(double);
  double (*p)(double);
  p=f;
  do
  {
    scanf("%lf%lf",&x1,&x2);
  }
  while((*p)(x1)*(*p)(x2)>0);//保证f(x1)和f(x2)是异号，这样才可以进行下一步的精准区间，否则，重新输入x1，x2的值
 
  printf("%.2lf\n",erfen(x1,x2,f));
  return 0;
}