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

public class codeforces {
	
	public static void main(String[] args) {
		FS scan = new FS(System.in);
		double r = scan.nextDouble(), x1 = scan.nextDouble(), y1 = scan.nextDouble(), x2 = scan.nextDouble(), y2 = scan.nextDouble();
		
		double d = Math.sqrt((y2-y1)*(y2-y1)+(x2-x1)*(x2-x1));
		
		System.out.println((long)Math.ceil(d/(2*r)));
	}

	private static long exp(long a, long b, long mod) {
		if(b==0)return 1;
		long t = exp(a,b/2,mod);
		return (b%2==0) ? (t*t)%mod:(a*((t*t)%mod))%mod;
	}
	private static class FS {
		BufferedReader br;
		StringTokenizer st;
		public FS(InputStream in) {
			br = new BufferedReader(new InputStreamReader(in));
		}
		String next(){
			while(st==null||!st.hasMoreElements()){
				try{st = new StringTokenizer(br.readLine());}
				catch(IOException e){e.printStackTrace();}
			}
			return st.nextToken();
		}
		int nextInt() {return Integer.parseInt(next());}
		long nextLong() {return Long.parseLong(next());}
		double nextDouble() { return Double.parseDouble(next());}
	}
}
