import java.io.*;
import java.util.*;

public class Task {
		
	public static void main(String[] args) throws IOException {
		new Task().solve();
	}
	
	PrintWriter out;
	int mul = 26+26+10;
	int nv = 4000;
	int[][] g;
	int[] pos;
	int cnt = 0;
	void solve() throws IOException{
		Reader in = new Reader("input.txt");
		out = new PrintWriter( new BufferedWriter(new OutputStreamWriter(System.out)) );
		//out = new PrintWriter(new FileWriter(new File("output.txt"))); 
			
		
		long r = in.nextInt();
		long x = in.nextInt();
		long y = in.nextInt();
		long dx = in.nextInt();
		long dy = in.nextInt();
		
		double d = Math.sqrt( (dx-x)*(dx-x) + (dy-y)*(dy-y) );
		
		double res = d/(r*2);
		
		out.print((int)Math.ceil(res));
		out.flush();
		out.close();
	}

}
	
	
	
	class Reader {
	    
	    StringTokenizer token;
	    BufferedReader in;
	    
	    public Reader(String file) throws IOException {
	        //in = new BufferedReader( new FileReader( file ) );
	        in = new BufferedReader( new InputStreamReader( System.in ) );
	    }
	    
	    public byte nextByte() throws IOException {
	        return Byte.parseByte(Next());
	    }
	    
	    public int nextInt() throws IOException {
	        return Integer.parseInt(Next());
	    }
	    
	    public long nextLong() throws IOException {
	        return Long.parseLong(Next());
	    }
	    
	    public String nextString() throws IOException {
	        return in.readLine();
	    }
	    
	    private String Next() throws IOException {
	        while (token == null || !token.hasMoreTokens()) {
	            token = new StringTokenizer(in.readLine());
	        }
	        return token.nextToken();
	    }

	    
	}

	
