import java.io.BufferedInputStream;
import java.io.IOException;
import java.math.BigDecimal;
import java.math.BigInteger;
import java.util.*;
import java.util.Map.Entry;

public class Main {
	public static final int C = 1000000007;
	static int MAP[][];
	static int W[][];
	//static int N;
	//static int M;

	public static void main(String[] args) {
		StringBuilder sb = new StringBuilder();
		BufferedInputStream bs = new BufferedInputStream(System.in);
		Scanner sc = new Scanner(bs);

		int r = sc.nextInt();
		
		int x = sc.nextInt();
		int y = sc.nextInt();
		int nx = sc.nextInt();
		int ny = sc.nextInt();
		
		
		int ans = 0;
		
		double dis = Math.hypot(x - nx, y - ny);
		
		ans = (int)Math.ceil(dis / (r*2));
		
	
		System.out.println(ans);
	}
	
}
