
import java.util.Scanner;
public class T3{
	
	
	
public static void main(String[] args) {
Scanner g = new Scanner(System.in);
//watermelon w =new watermelon();
int r = g.nextInt();
int x = g.nextInt();
int  y= g.nextInt();
int x1 = g.nextInt();
int y1 = g.nextInt();
int d=0;
int p=0;
d = ((x1-x)^2 + (y1-y)^2)^(1/2);

if(d>(2*r)  ){
	p = d/(2*r);
	p = p+1;
}
else if(d == (2*r)){
	p=1;
}
else if(d == 0){
	p=0;
}
else{
	p=1;
}
System.out.println(p);
}
}

