import java.util.*;

public class amrAndPins {
	
	public static float dist(int x, int y, int x1, int y1) {
		float result = (x-x1)*(x-x1) + (y-y1)*(y-y1);
		result = (float)Math.sqrt(result);
		return result;
	}

	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();
		
		float dis = dist(x, y, x1, y1);
		int result = 0;
		result += (int)dis / (2*n);
		if((float)(2*n*result) < dis)
			result++;
		System.out.print(result);
	}

}
