import java.io.*;
import java.util.StringTokenizer;
public class CF0507B
{
 public static void main(String[] helloWorld) throws IOException
 {
  BufferedReader sIn = new BufferedReader(new InputStreamReader(System.in));
  StringTokenizer sT = new StringTokenizer(sIn.readLine());
  int[] data = new int[5];
  for (int i = 0; i < 5; i ++)
   data[i] = Integer.parseInt(sT.nextToken());
  long dx = data[1] - data[3];
  long dy = data[2] - data[4];
  long ssquared = dx * dx + dy * dy;
  int n = (int) (Math.sqrt(ssquared) / 2 / data[0]);
  int d = (4L * data[0] * data[0] * n * n == ssquared) ? 0 : 1;
  System.out.println(n + d);
 }
}
