C :

#include <stdio.h>
#include <math.h>
int main()
{
  double a, x, y;
  scanf("%lf %lf", &a, &x);
  y = x + 1;
  while(fabs(x - y) >= 0.00001)
  {
    y = x;
	x = (y + a / y)/2.0;
  }
  printf("%.6lf\n", x);
  return 0;
}

C++ :

#include<stdio.h>
#include<math.h>

int main()  
{
  float x0,x1,a;  
  scanf("%f",&a); 
  x1=a/2;  
  do  
  {
    x0=x1;x1=(x0+a/x0)/2;
  }  
  while(fabs(x0-x1)>=0.00001); 
  printf("%f\n",x1); 
}