/**
 *
 * @author ABHISHEK SHANKHADHAR
 */
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.InputMismatchException;
public class practice 
{
    InputStream obj;
    PrintWriter out;
    String check="";
    public static void main(String[] args)throws IOException{
        new practice().ace();
    }
    //Solution !!
    void solution()
    {
        int r=inti(), x=inti(),y=inti(),xa=inti(),ya=inti();
        double u=Math.sqrt(((xa-x)*(xa-x))+((ya-y)*(ya-y)));
        double k=u/(2*r);
        k=Math.ceil(k);
        out.println((int)k);
    }
    //------->ends !!
    void ace()throws IOException{
        out=new PrintWriter(System.out);
        obj=check.isEmpty() ? System.in : new ByteArrayInputStream(check.getBytes());
        solution();
        out.flush();
        out.close();
    }
    byte inbuffer[]=new byte[1024];
    int lenbuffer=0,ptrbuffer=0;
    int readByte(){
        if(lenbuffer==-1)
            throw new InputMismatchException();
        if(ptrbuffer>=lenbuffer)
        {
            ptrbuffer=0;
            try {
                lenbuffer=obj.read(inbuffer);
            } catch (IOException e) {
                throw new InputMismatchException();
            }
        }
        if(lenbuffer<=0)
            return -1;
        return inbuffer[ptrbuffer++];
    }
    boolean isSpaceChar(int c)
    {
        return (!(c>=33 && c<=126));
    }
    
    String stri()
    {
        int b=skip();
        StringBuilder sb=new StringBuilder();
        while(!(isSpaceChar(b))) // when nextLine, (isSpaceChar(b) && b!=' ')
        {
            sb.appendCodePoint(b);
            b=readByte();
        }
        return sb.toString();
    }
    int skip()
    {
        int b;
        while((b=readByte())!=-1 && isSpaceChar(b));
        return b;
    }
    int inti()
    {
        int num = 0, b;
        boolean minus = false;
        while((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'));
        if(b == '-')
        {
            minus = true;
            b = readByte();
        }
        while(true)
        {
            if(b >= '0' && b <= '9')
            {
                num = num * 10 + (b - '0');
            }
            else
            {
                return minus ? -num : num;
            }
            b = readByte();
        }
    }
    long loni()
    {
        long num = 0;
        int b;
        boolean minus = false;
        while((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'));
        if(b == '-')
        {
            minus = true;
            b = readByte();
        }
        while(true)
        {
            if(b >= '0' && b <= '9')
            {
                num = num * 10 + (b - '0');
            }
            else
            {
                return minus ? -num : num;
            }
            b = readByte();
        }
    }
    float fl()
    {
        return Float.parseFloat(stri());
    }
    double dou()
    {
        return Double.parseDouble(stri());
    }
    char chi()
    {
        return (char)skip();
    }
    int[] arri(int n)
    {
        int a[]=new int[n];
        for(int i=0;i<n;i++)
            a[i]=inti();
        return a;
    }
    long[] arrl(int n)
    {
        long a[]=new long[n];
        for(int i=0;i<n;i++)
            a[i]=loni();
        return a;
    }
    String[] stra(int n)
    {
        String a[]=new String[n];
        for(int i=0;i<n;i++)
            a[i]=stri();
        return a;
    }
}
