import java.util.Scanner;


public class B {

public static void main(String[] args) {
	Scanner sc = new Scanner(System.in);
	int r = sc.nextInt();
	int x = sc.nextInt();
	int y= sc.nextInt();
	int xx = sc.nextInt();
	int yy = sc.nextInt();
	
	double dist = Math.sqrt(1.0*(x-xx)*(x-xx)+1.0*(y-yy)*(y-yy));
	int ans = (int)(dist/(2.0*r));
	if(ans*2.0*r < dist)
		ans++;
	System.out.println(ans);
}
	
}
