Amr loves Geometry. One day he came up with a very interesting problem.

Amr has a circle of radius r and center in point (x, y). He wants the circle center to be in new position (x', y').

In one step Amr can put a pin to the border of the circle in a certain point, then rotate the circle around that pin by any angle and finally remove the pin.

Help Amr to achieve his goal in minimum number of steps.

Input

Input consists of 5 space-separated integers r, x, y, x' y' (1 ≤ r ≤ 105,  - 105 ≤ x, y, x', y' ≤ 105), circle radius, coordinates of original center of the circle and coordinates of destination center of the circle respectively.

Output

Output a single integer — minimum number of steps required to move the center of the circle to the destination point.

Examples

Input

2 0 0 0 4


Output

1


Input

1 1 1 4 4


Output

3


Input

4 5 6 5 6


Output

0

Note

In the first sample test the optimal way is to put a pin at point (0, 2) and rotate the circle by 180 degrees counter-clockwise (or clockwise, no matter).

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import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;
import java.lang.*;

public class P507B {
    //static long m=1000000007;
    static BigInteger ways(int N,  int K) {
        BigInteger ret = BigInteger.ONE;
        for(int i=N;i>=N-K+1;i--)
        {
             ret = ret.multiply(BigInteger.valueOf(i));
            
        }
        for (int j = 1; j<=K; j++) {
            ret = ret.divide(BigInteger.valueOf(j));
        }
       
            ret=ret.mod(BigInteger.valueOf(1000000007));
        
        return ret;
    }
    public static int prime(int n)
    {
        int f=1;
        if(n==1)
            return 0;
        for(int i=2;i<=(Math.sqrt(n));)
        {
            if(n%i==0)
            {
                f=0;
                break;
            }
            if(i==2)
                i++;
            else
                i+=2;
        }
        if(f==1)
            return 1;
        else 
            return 0;
    }
public static long gcd(long x,long y)
{
    if(x%y==0)
        return y;
    else return gcd(y,x%y);
}
    public static BigInteger fact(int n)
    {
        BigInteger f=BigInteger.ONE;
        for(int i=1;i<=n;i++)
        {
            f=f.multiply(BigInteger.valueOf(i));
        }
        //f=f.mod(BigInteger.valueOf(m));
        return f;
    }
public static int gcd(int x,int y)
{
    if(x%y==0)
        return y;
    else return gcd(y,x%y);
}
public static int max(int a,int b)
{
    if(a>b)
        return a;
    else
        return b;
}
public static int min(int a,int b)
{
    if(a>b)
        return b;
    else 
        return a;
}
public static long max(long a,long b)
{
    if(a>b)
        return a;
    else
        return b;
}
public static long min(long a,long b)
{
    if(a>b)
        return b;
    else 
        return a;
}
public static long pow(long n,long p,long m)
{
     long  result = 1;
      if(p==0)
        return 1;
    if (p==1)
        return n;
    while(p!=0)
    {
        if(p%2==1)
            result *= n;
        result%=m;
        p >>=1;
        n*=n;
        n%=m;
    }
    return result;
}
static long ncr(long n,long k)
{
    long w=1;
    for(long i=n,j=1;i>=n-k+1;i--,j++)
    {
        w=w*i;
        w=w/j;
        w%=1000000007;
        
    }
    return w;
}
static class Pair implements Comparable<Pair>
{
    int a,b;
    Pair (int a,int b)
    {
        this.a=a;
        this.b=b;
    }

    public int compareTo(Pair o) {
        // TODO Auto-generated method stub
        if(this.a!=o.a)
        return Integer.compare(this.a,o.a);
        else
            return Integer.compare(this.b, o.b);
        //return 0;
    }
}

    public static void main(String[] args) throws Exception{
        
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        StringBuilder sb=new StringBuilder("");
         //InputReader in = new InputReader(System.in);
        // OutputWriter out = new OutputWriter(System.out);
        //PrintWriter pw=new PrintWriter(System.out);
        //String line=br.readLine().trim();
        //int t=Integer.parseInt(br.readLine());
    //  while(t-->0)
        //{
        //int n=Integer.parseInt(br.readLine());
        //long n=Long.parseLong(br.readLine());
        //line=br.readLine().trim();
        //String l[]=br.readLine().split(" ");
        //int m=Integer.parseInt(l[0]);
        //int k=Integer.parseInt(l[1]);
        //l=br.readLine().split(" ");
        //long m=Long.parseLong(l[0]);
        //long n=Long.parseLong(l[1]);
        //char ch=a.charAt();
    //  char c[]=new char[n];
        //String l[]=br.readLine().split(" ");
        //l=br.readLine().split(" ");
        /*int a[]=new int[n];
        for(int i=0;i<n;i++)
        {
            a[i]=Integer.parseInt(l[i]);
        }*/
        /*long a[]=new long[n];
        for(int i=0;i<n;i++)
        {
            a[i]=Long.parseLong(l[i]);
        }*/
        /*int a[][]=new int[n][n];
        for(int i=0;i<n;i++)
        {
        l=br.readLine().split(" ");
            for(int j=0;j<n;j++)
            {
                a[i][j]=Long.parseLong(l[j]);
            }
        }*/
        
        //  String a=br.readLine();
        
        // char a[]=c.toCharArray();
        //char ch=l[0].charAt(0);
        
        
          // int f1[]=new int[26];
           //int f2[]=new int[26];
        /*for(int i=0;i<n;i++)
        {
        int x=a.charAt(0);
            f1[x-97]++;
        }*/
        /*for(int i=0;i<n;i++)
        {
            
        }*/
        /*for(int i=0;i<n;i++)
        {
            for(int j=0;j<n;j++)
            {
                
            }
        }*/
        /*while(q--)
          {
                l=br.readLine().split(" ");
                int n=Integer.parseInt(l[0]);
                int k=Integer.parseInt(l[1]);
          }
         */
        /*if(f==1)
            System.out.println("Yes");
        else
            System.out.println("No");*/
        //System.out.print("");
        //sb.append("");
        //sb.append("").append("\n");
        
        String l[]=br.readLine().split(" ");
        int r=Integer.parseInt(l[0]);
        int x1=Integer.parseInt(l[1]);
        int y1=Integer.parseInt(l[2]);
        int x2=Integer.parseInt(l[3]);
        int y2=Integer.parseInt(l[4]);
        int max=0;
        double x=Math.abs(x2-x1);
        double y=Math.abs(y2-y1);
        x=x*x;
        y=y*y;
        double z=Math.sqrt(x+y);
        double h=2*r;
        //System.out.println(z+" "+h);
        double a=Math.ceil(z/h);
        int f=(int)a;
           System.out.println(f);           
        
        //}
    }
   static  class InputReader
    {
        private InputStream stream;
        private byte[] buf = new byte[1024];
        private int curChar;
        private int numChars;
        private SpaceCharFilter filter;

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

        public int read()
        {
            if (numChars == -1)
                throw new InputMismatchException();
            if (curChar >= numChars)
            {
                curChar = 0;
                try
                {
                    numChars = stream.read(buf);
                } catch (IOException e)
                {
                    throw new InputMismatchException();
                }
                if (numChars <= 0)
                    return -1;
            }
            return buf[curChar++];
        }

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

        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 double readDouble() {
            int c = read();
            while (isSpaceChar(c))
                c = read();
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            double res = 0;
            while (!isSpaceChar(c) && c != '.') {
                if (c == 'e' || c == 'E')
                    return res * Math.pow(10, readInt());
                if (c < '0' || c > '9')
                    throw new InputMismatchException();
                res *= 10;
                res += c - '0';
                c = read();
            }
            if (c == '.') {
                c = read();
                double m = 1;
                while (!isSpaceChar(c)) {
                    if (c == 'e' || c == 'E')
                        return res * Math.pow(10, readInt());
                    if (c < '0' || c > '9')
                        throw new InputMismatchException();
                    m /= 10;
                    res += (c - '0') * m;
                    c = read();
                }
            }
            return res * sgn;
        }
        public long readLong() {
            int c = read();
            while (isSpaceChar(c))
                c = read();
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            long res = 0;
            do {
                if (c < '0' || c > '9')
                    throw new InputMismatchException();
                res *= 10;
                res += c - '0';
                c = read();
            } while (!isSpaceChar(c));
            return res * sgn;
        }
        public boolean isSpaceChar(int c)
        {
            if (filter != null)
                return filter.isSpaceChar(c);
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }

        public String next()
        {
            return readString();
        }

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

     static class OutputWriter
    {
        private final PrintWriter writer;

        public OutputWriter(OutputStream outputStream)
        {
            writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
        }

        public OutputWriter(Writer writer)
        {
            this.writer = new PrintWriter(writer);
        }

        public void print(Object... objects)
        {
            for (int i = 0; i < objects.length; i++)
            {
                if (i != 0)
                    writer.print(' ');
                writer.print(objects[i]);
            }
        }

        public void printLine(Object... objects)
        {
            print(objects);
            writer.println();
        }

        public void close()
        {
            writer.close();
        }

        public void flush()
        {
            writer.flush();
        }

    }
    /* USAGE

    //initialize
        InputReader in      = new InputReader(System.in);
        OutputWriter out    =   new OutputWriter(System.out);

    //read int
    int i = in.readInt();
    //read string
    String s = in.readString();
    //read int array of size N
    int[] x = IOUtils.readIntArray(in,N);
    //printline
    out.printLine("X");


    //flush output
    out.flush();

    //remember to close the
    //outputstream, at the end
    out.close();

    */
  static   class IOUtils {

        public static int[] readIntArray(InputReader in, int size) {
            int[] array = new int[size];
            for (int i = 0; i < size; i++)
                array[i] = in.readInt();
            return array;
    }
    }
}