//https://codeforces.com/problemset/problem/507/B
//B. Amr and Pins
import java.util.*;
import java.io.*;
public class CF_507_B{
	public static void main(String[] args) throws Exception{
		
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		PrintWriter pw = new PrintWriter(new OutputStreamWriter(System.out));
		StringBuilder sb = new StringBuilder();
		StringTokenizer st;

		st = new StringTokenizer(br.readLine().trim());
		long r = 2*Integer.parseInt(st.nextToken());
		long x = Integer.parseInt(st.nextToken());
		long y = Integer.parseInt(st.nextToken());
		long x1 = Integer.parseInt(st.nextToken());
		long y1 = Integer.parseInt(st.nextToken());

		double dis = Math.sqrt((x1-x)*(x1-x)+(y1-y)*(y1-y));

		long ans = (long)Math.ceil(dis/r);
		sb.append(ans);

		pw.print(sb);
		pw.flush();
		pw.close();
	}
}