C :

#include <stdio.h>
#include <stdlib.h>
#define p 1e-6
int main(int argc, char *argv[])
{
  float m,x;
  scanf("%f",&m);
  x=m;
  while(fabs(x*x-m)>=p)
  x=0.5f*(x+m/x);
  printf("%.3f\n",x);

  return 0;
}

C++ :

#include<iostream>
#include<cmath>
#include<cstdio>
using namespace std;
int main()
{
	double a,x0,x1;
	cin>>a;
	x0=a/2;
	x1=(x0+a/x0)/2;
	while (fabs(x1-x0)>1e-5)
	{
		x0=x1;
		x1=(x0+a/x0)/2;
	}
	printf("%.3lf\n",x1);
	return 0;
}

Pascal :

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