import java.util.*;
public class Main
{
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int radius = scan.nextInt();
		int x = scan.nextInt();
		int y = scan.nextInt();
		int dx = scan.nextInt();
		int dy = scan.nextInt();
		//double xmoves = dx/(radius*2);
		//double ymoves = dy/(radius*2);
		double moves = Math.sqrt((dx - x) * (dx-x) + (dy - y) * (dy - y))/(radius*2);
		System.out.println((int)moves);
	}
}
