import java.util.Scanner;

public class amrandpins {

    public static void main(String[] args) {

        long x, y, xi, yi, r;

        Scanner sc = new Scanner(System.in);
        r = sc.nextLong();
        x = sc.nextLong();
        y = sc.nextLong();
        xi = sc.nextLong();
        yi = sc.nextLong();

        double dist = Math.sqrt((x - xi) * (x - xi) + (y - yi) * (y - yi));
        double ans = dist / (2 * r);
        
        if(ans == Math.floor(ans))
            System.out.println((int)ans);
        else 
            System.out.println((int)Math.floor(ans) + 1);
    } 
}