import java.io.*;
import java.util.Arrays;
import java.util.InputMismatchException;
import java.util.Random;

public class Q1{
	static class InputReader {

		private final InputStream stream;
		private final byte[] buf = new byte[8192];
		private int curChar, snumChars;
		private String[] s;
		public InputReader(InputStream st) {
			this.stream = st;
		}
		public int read() {
			if (snumChars == -1)
				throw new InputMismatchException();
			if (curChar >= snumChars) {
				curChar = 0;
				try {
					snumChars = stream.read(buf);
				} catch (IOException e) {
					throw new InputMismatchException();
				}
				if (snumChars <= 0)
					return -1;
			}
			return buf[curChar++];
		}

		public int nextInt() {
			int c = read();
			while (isSpaceChar(c)) {
				c = read();
			}
			int sgn = 1;
			if (c == '-') {
				sgn = -1;
				c = read();
			}
			int res = 0;
			do {
				res *= 10;
				res += c - '0';
				c = read();
			} while (!isSpaceChar(c));
			return res * sgn;
		}

		public long nextLong() {
			int c = read();
			while (isSpaceChar(c)) {
				c = read();
			}
			int sgn = 1;
			if (c == '-') {
				sgn = -1;
				c = read();
			}
			long res = 0;
			do {
				res *= 10;
				res += c - '0';
				c = read();
			} while (!isSpaceChar(c));
			return res * sgn;
		}

		public int[] nextIntArray(int n) {
			int a[] = new int[n];
			s=nextLine().split(" ");
			for (int i = 0; i < n; i++) {
				a[i] = Integer.parseInt(s[i]);
			}
			return a;
		}

		public String readString() {
			int c = read();
			while (isSpaceChar(c)) {
				c = read();
			}
			StringBuilder res = new StringBuilder();
			do {
				res.appendCodePoint(c);
				c = read();
			} while (!isSpaceChar(c));
			return res.toString();
		}

		public String nextLine() {
			int c = read();
			while (isSpaceChar(c))
				c = read();
			StringBuilder res = new StringBuilder();
			do {
				res.appendCodePoint(c);
				c = read();
			} while (!isEndOfLine(c));
			return res.toString();
		}

		public boolean isSpaceChar(int c) {
			return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
		}

		private boolean isEndOfLine(int c) {
			return c == '\n' || c == '\r' || c == -1;
		}

	}
	static InputReader sc=new InputReader(System.in);
	static PrintWriter out=new PrintWriter(System.out);

	public final long MOD = (long) 1e9 + 7;

	static boolean isInteger(double n) {
		return (n-(int)n==0);
	}
	static int ans(int r,int x,int y,int a,int b){
		int dx=Math.abs(x-a);
		dx*=dx;
		int dy=Math.abs(y-b);
		dy*=dy;
		double d=Math.sqrt(dy+dx);
		r<<=1;
		return (isInteger(d) && d%r==0)?(int)d/r:(int)(d/r)+1;
	}
	public static void main(String[] args)throws IOException {
//		int n,l;
//		String s;
//		int[] num;
//		double d;
//		Random rand=new Random();
//		while(t-->0) {
//			n=nextInt();
//			l=nextInt();
//			num=nextIntArray(n);
//			d=ans(n,l,num);
			println(ans(nextInt(),nextInt(),nextInt(),nextInt(),nextInt()));
//		}
		out.flush();
	}


	public static int nextInt()throws IOException{
		return sc.nextInt();
	}
	public static long nextLong()throws IOException
	{
		return sc.nextLong();
	}
	public static double nextDouble()throws IOException
	{
		return Double.parseDouble(readString());
	}
	public static String readString()throws IOException
	{
		return sc.readString();
	}
	public static String nextLine()throws IOException{
		return sc.nextLine();
	}
	public static int[] nextIntArray(int n)throws IOException{
		return sc.nextIntArray(n); 
	}
	public static long[] nextLongArray(int n)throws IOException{
		long[] array=new long[n];
		String[] s=nextLine().split(" ");
		for(int i=0;i<n;i++) {
			array[i]=Long.parseLong(s[i]);
		}
		return array;
	}
	public static void printSp(Object a)throws IOException{
		out.print(a+" ");
	}
	public static void println(Object a)throws IOException{
		out.println(a);
	}
	public static void printArray(int[] a)throws IOException{
		for(int i=0;i<a.length;i++)
			printSp(a[i]);
	}


}