import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Random;
import java.util.StringTokenizer;
import java.util.TreeMap;
import java.util.TreeSet;
import java.util.concurrent.ThreadLocalRandom;

public class zizo {
	
	public static void main(String[]args) throws IOException {
		Scanner zizo=new Scanner(System.in);
		PrintWriter wr=new PrintWriter(System.out);
		
		int r=zizo.nextInt()*2;
		int x=zizo.nextInt();
		int y=zizo.nextInt();
		int x1=zizo.nextInt();
		int y1=zizo.nextInt();
		int d=(int)(1.0*Math.sqrt(1.0*(x1-x)*(x1-x)+(y1-y)*(y1-y))/r);
		if((Math.sqrt(1.0*(x1-x)*(x1-x)+(y1-y)*(y1-y))%r)!=0)d++;
		wr.println(d);
				
		wr.close();
	}
	static void shuffleArray(int[] ar)
	{
		// If running on Java 6 or older, use `new Random()` on RHS here
		Random rnd = ThreadLocalRandom.current();
		for (int i = ar.length - 1; i > 0; i--)
		{
			int index = rnd.nextInt(i + 1);
			// Simple swap
			int a = ar[index];
			ar[index] = ar[i];
			ar[i] = a;
		}
	}
}
class edge {
	int v,w;
	edge(int a,int b){v=a;w=b;}
}
class Scanner 
{
	StringTokenizer st;
	BufferedReader br;

	public Scanner(InputStream s){br = new BufferedReader(new InputStreamReader(s));}

	public String next() throws IOException 
	{
		while (st == null || !st.hasMoreTokens()) 
			st = new StringTokenizer(br.readLine(), ",| ");
		return st.nextToken();
	}

	public int nextInt() throws IOException {return Integer.parseInt(next());}

	public long nextLong() throws IOException {return Long.parseLong(next());}

	public String nextLine() throws IOException {return br.readLine();}

	public boolean ready() throws IOException {return br.ready();}

	public double nextDouble() throws IOException 
	{
		String x = next();
		StringBuilder sb = new StringBuilder("0");
		double res = 0, f = 1;
		boolean dec = false, neg = false;
		int start = 0;
		if(x.charAt(0) == '-')
		{
			neg = true;
			start++;
		}
		for(int i = start; i < x.length(); i++)
			if(x.charAt(i) == '.')
			{
				res = Long.parseLong(sb.toString());
				sb = new StringBuilder("0");
				dec = true;
			}
			else
			{
				sb.append(x.charAt(i));
				if(dec)
					f *= 10;
			}
		res += Long.parseLong(sb.toString()) / f;
		return res * (neg?-1:1);
	}

}
