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


public class AmrAndPins {
public static void main(String[] args) throws IOException {
    BufferedReader bf = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer st = new StringTokenizer(bf.readLine());
    int r = Integer.parseInt(st.nextToken());
    long x1 = Integer.parseInt(st.nextToken());
    long y1 = Integer.parseInt(st.nextToken());
    long x2 = Integer.parseInt(st.nextToken());
    long y2 = Integer.parseInt(st.nextToken());
    long subd = ((y2-y1)*(y2-y1))+((x2-x1)*(x2-x1));
    double d = Math.sqrt(subd);
    int result = (int) Math.ceil(d/(2*r));
    System.out.println(result);
} 
}
