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

/**
 * 

 0  0
------
 0  2
 0 -2
 2  0
-2  0
------
  
 1  1
------
 1  2
 1  0
 0  1
 1  0
 * */
public class B_Div2_287 {
    public static void main(String[]arg) throws IOException
    {
        new B_Div2_287().solve();
    }
    public void solve()throws IOException
    {
        BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer(in.readLine());
        int ans,r,x,y,xp,yp,d;
        r = Integer.parseInt(st.nextToken());
        x = Integer.parseInt(st.nextToken());
        y = Integer.parseInt(st.nextToken());
        xp = Integer.parseInt(st.nextToken());
        yp = Integer.parseInt(st.nextToken());
        if(x == xp && y == yp)
        {
            System.out.println("0");
        }
        else
        {
            d = (int)Math.ceil(Math.sqrt((x-xp)*(x-xp) + (y-yp)*(y-yp))/(double)(2*r)); 
            System.out.println(d);
        }
    }
}
