import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.*;

public class Main
{
    public static double getDistance(double x, double y, double x1, double y1)
    {
        double xD = x1 - x;
        double yD = y1 - y;
        return Math.sqrt( xD * xD + yD * yD );
    }
    public static void main(String args[])
    {
        MyScanner scanner = new MyScanner();
        int turns = 0;
        double r = scanner.nextInt(), x = scanner.nextInt(), y = scanner.nextInt() , x1 = scanner.nextInt(), y1 = scanner.nextInt();
        double distance = getDistance(x, y, x1, y1 );
        while ( distance >= 2 * r )
        {
            distance -= (2 * r);
            turns++;
        }
        if( distance > r )
        {
            turns++;
        }
        turns++;
        System.out.println(turns);
    }
}


class MyScanner {
    BufferedReader br;
    StringTokenizer st;

    public MyScanner() {
        br = new BufferedReader(new InputStreamReader(System.in));
    }

    public int mod(long x) {
        // TODO Auto-generated method stub
        return (int) x % 1000000007;
    }

    public int mod(int x) {
        return x % 1000000007;
    }

    boolean hasNext() {
        if (st.hasMoreElements())
            return true;
        try {
            st = new StringTokenizer(br.readLine());
        } catch (IOException e) {
            e.printStackTrace();
        }
        return st.hasMoreTokens();
    }

    String next() {
        while (st == null || !st.hasMoreElements()) {
            try {
                st = new StringTokenizer(br.readLine());
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        return st.nextToken();
    }

    int nextInt() {
        return Integer.parseInt(next());
    }

    double nextDouble() {
        return Double.parseDouble(next());
    }

    String nextLine() {
        String str = "";
        try {
            str = br.readLine();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return str;
    }

    public long nextLong() {
        return Long.parseLong(next());
    }
}