C :

#include<stdio.h>
#include<math.h>
int main()
{
	double a, x2, x1;
	scanf("%lf", &a);
	x2 = 1.0;
	do
	{
		x1 = x2;
		x2 = 0.5 * (x1 + a / x1);
	}
	while(fabs(x1 - x2) >= 1e-5);
	printf("%.3lf\n", x2);
	return 0;
}

C++ :

#include<iostream>
#include<stdio.h>
#include<math.h>
using namespace std;
int main()
{
 double x1,x2,a;
cin>>a;
 if(a>=0)
 { 
  x2=1.0;
  do
  {
   x1=x2;
   x2=0.5*(x1+a/x1);
  }
  while(fabs(x2-x1)>=1e-5);
  printf("%.3f\n",x2);
 }
 return 0;
}

Pascal :

var s:longint;
begin
  readln(s);
  writeln(sqrt(s):0:3);
end.