import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.StringTokenizer;

public class TB {

	public static void main(String[] args) {
		FastScanner in=new FastScanner();
		long r,x,y,x1,y1;
		r=in.nextLong();
		x=in.nextLong();
		y=in.nextLong();
		x1=in.nextLong();
		y1=in.nextLong();
		long res=(long)Math.ceil(Math.sqrt((x-x1)*(x-x1)+(y-y1)*(y-y1))/(2*r));
		System.out.println(res);
	}
	static class FastScanner{
		BufferedReader br;
		StringTokenizer st;
		public FastScanner(){br=new BufferedReader(new InputStreamReader(System.in));}
		String nextToken(){
			while(st==null||!st.hasMoreElements())
				try{st=new StringTokenizer(br.readLine());}catch(Exception e){}
			return st.nextToken();
		}
		int nextInt(){return Integer.parseInt(nextToken());}
		long nextLong(){return Long.parseLong(nextToken());}
		double nextDouble(){return Double.parseDouble(nextToken());}
	}
}
