import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.math.BigInteger;
import java.util.StringTokenizer;


public class B {
    
    public static void main(String[] args) throws IOException {
        br = new BufferedReader( new InputStreamReader(System.in) );
        out = new PrintWriter(System.out);
        st = new StringTokenizer("");
        sb = new StringBuilder();
        
        double r = nxtDbl();
        double x1 = nxtDbl();
        double y1 = nxtDbl();
        double x2 = nxtDbl();
        double y2 = nxtDbl();
        double x = x1-x2;
        double dist = Math.sqrt( Math.pow(x1-x2, 2) + Math.pow(y1-y2, 2) );
        
        int res = (int) ((dist / r) - 1);
        if( dist == 0){
            res = 0;
        }
        System.out.println( res );
        
        
    }//end main.

    
    static BufferedReader br;
    static StringTokenizer st;
    static StringBuilder sb;
    static PrintWriter out;
    static FileReader fr;
    static FileWriter fw;
    static BufferedWriter bw;

    static String nxtTok() throws IOException {
        while (!st.hasMoreTokens()) {
            String s = br.readLine();
            if (s == null)
                return null;
            st = new StringTokenizer(s.trim());
        }
        return st.nextToken();
    }

    static int nxtInt() throws IOException {
        return Integer.parseInt(nxtTok());
    }

    static long nxtLng() throws IOException {
        return Long.parseLong(nxtTok());
    }

    static double nxtDbl() throws IOException {
        return Double.parseDouble(nxtTok());
    }

    static int[] nxtIntArr(int n) throws IOException {
        int[] a = new int[n];
        for (int i = 0; i < n; i++)
            a[i] = nxtInt();
        return a;
    }

    static long[] nxtLngArr(int n) throws IOException {
        long[] a = new long[n];
        for (int i = 0; i < n; i++)
            a[i] = nxtLng();
        return a;
    }

    static char[] nxtCharArr() throws IOException {
        return nxtTok().toCharArray();
    }
    
        
}//end class.