import java.util.*;
import java.lang.*;
import java.io.*;
public class amrPins{
    public static void main(String[] args) {

        Scanner fi=new Scanner(System.in);
        PrintWriter pr=new PrintWriter(System.out);

        int i=0,j=0;
        int r=fi.nextInt();
        int x=fi.nextInt();
        int y=fi.nextInt();
        int x1=fi.nextInt();
        int y1=fi.nextInt();
        int steps=0;

        int value=(int)Math.pow((x-x1),2)+(int)Math.pow((y-y1),2);
        double dist=Math.sqrt(value);

        if(dist%(2*r)==0)
        {
            if((x==x1)&&(y==y1))
                steps=0;
            else
                steps=(int)(dist/(2*r));
        }
        else
        {
            if(dist>r)
                steps=(int)(dist/(2*r))+1;
            else
                steps=2;
        }

        pr.println(steps);
        fi.close();
        pr.close();

    }

}



 class InputReader {
 private InputStream stream;
 private byte[] buf = new byte[8192];
 private int curChar, snumChars;
 private SpaceCharFilter filter;

 public InputReader(InputStream stream) {
 this.stream = stream;
 }

 public int snext() {
 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 = snext();
 while (isSpaceChar(c))
 c = snext();
 int sgn = 1;
 if (c == '-') {
 sgn = -1;
 c = snext();
 }
 int res = 0;
 do {
 if (c < '0' || c > '9')
 throw new InputMismatchException();
 res *= 10;
 res += c - '0';
 c = snext();
 } while (!isSpaceChar(c));
 return res * sgn;
 }

 public long nextLong() {
 int c = snext();
 while (isSpaceChar(c))
 c = snext();
 int sgn = 1;
 if (c == '-') {
 sgn = -1;
 c = snext();
 }
 long res = 0;
 do {
 if (c < '0' || c > '9')
 throw new InputMismatchException();
 res *= 10;
 res += c - '0';
 c = snext();
 } while (!isSpaceChar(c));
 return res * sgn;
 }

 public int[] nextIntArray(int n) {
 int a[] = new int[n+1];
 for (int i = 1; i <= n; i++)
 a[i] = nextInt();
 return a;
 }

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

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

 public interface SpaceCharFilter {
 public boolean isSpaceChar(int ch);
 }
 }
