import java.util.*;

public class amrAndPins {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		int n = sc.nextInt();
		int x = sc.nextInt();
		int y = sc.nextInt();
		int x1 = sc.nextInt();
		int y1 = sc.nextInt();
		sc.close();

		double dist = Math.sqrt((long)(x-x1)*(long)(x-x1) + (long)(y-y1)*(long)(y-y1));
		long result = (long)dist / (long)(2*n);
		if(2*n*result < dist)
			result++;
		System.out.print(result);
	}

}
