#include <iostream>
#include <math.h>
using namespace std;

double Grial(int x)
{
	double result = 1;
	double num = x;
	do{
			result = num;
			num = result/2.0+x/2.0/result;
		}while(fabs(num-result)>0.00001);
	return result;
}
//牛顿迭代公式x(n+1)=x(n）－f(x(n))/f‘(x(n))
//求N的平方根就是求f(x)=N-x^2=0的解
//x1=x2;
//然后就是x2 = x1-(N-x1^2)/(-2x1)=x1/2.0+N/2.0/x1
int main()
{
	cout<<Grial(3)<<endl;
	return 0;
}