import java.io.*;
import java.util.*;
public class div287B
{
	BufferedReader in;
	PrintWriter ob;
	StringTokenizer st;
	public static void main(String[] args) throws IOException {
		new div287B().run();
	}
	void run() throws IOException {
		in=new BufferedReader(new InputStreamReader(System.in));
		ob=new PrintWriter(System.out);
		solve();
		ob.flush();
	}
	void solve() throws IOException {
		int r=ni();
		int x=ni();
		int y=ni();
		int x2=ni();
		int y2=ni();
		double dist=(double)Math.sqrt((x2-x)*1L*(x2-x)+(y2-y)*1L*(y2-y));
		double deno=2.0*r;
		ob.println((int)Math.ceil(dist/deno));
	}
	int ni() throws IOException{
		return Integer.parseInt(nextToken());
	}
	double nd() throws IOException {
		return Double.parseDouble(nextToken());
	}
	String nextToken() throws IOException {
		if(st==null || !st.hasMoreTokens())
			st=new StringTokenizer(in.readLine());
		return st.nextToken();
	}
}