
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.StringTokenizer;

public class B507 {

    public static void main(String[] args) throws IOException {
        BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
        PrintWriter out = new PrintWriter(new OutputStreamWriter(System.out));
        StringTokenizer st = new StringTokenizer(in.readLine());
        int r = Integer.parseInt(st.nextToken());
        int x = Integer.parseInt(st.nextToken());
        int y = Integer.parseInt(st.nextToken());
        int x0 = Integer.parseInt(st.nextToken());
        int y0 = Integer.parseInt(st.nextToken());
        r *= 2;
        double d = Math.sqrt(Math.pow(x - x0 , 2) + Math.pow(y - y0 , 2));
        int res = 0;
        while (res * r < d) 
            res++;
        out.println(res);
        out.close();
    }

}
