import java.util.Scanner;

public class Main {
	static Scanner s;

	

	public static void main(String[] args) {
		{int n=5;
		int steps=0;
		 s= new Scanner(System.in);
		int a[]=new int[5];
		
			for(int i=0;i<n;i++)
			{a[i]=s.nextInt();}
			double distance=Math.sqrt(Math.pow(a[3]-a[1], 2)+Math.pow(a[4]-a[2],2));
			//System.out.println(distance);
 
			if((int)distance==0)
				{steps=0;}
			 else if(distance>0)
			{
			while(distance>0)
			{
			steps++;
			distance=distance-2*a[0];				
			}
			}
System.out.println(steps);
		}
	}

}
