import java.util.Scanner;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Scanner;

public class Rough {
		
	public static void main(String[] args) {
		Scanner s=new Scanner(System.in);
		double r= s.nextDouble();
		double x= s.nextDouble();
		double y= s.nextDouble();
		double m= s.nextDouble();
		double n= s.nextDouble();
		
		double dist = Math.sqrt((m-x)*(m-x) + (n-y)*(n-y));
		int val = (int)Math.ceil(dist/2.0/r);
		System.out.println(val);
		
		
		}
}