import java.util.*;
import java.lang.*;
import java.io.*;
public class Codechef
{   static PrintWriter out=new PrintWriter(System.out);
	static FastScanner in = new FastScanner(System.in);
     static class FastScanner {BufferedReader br;StringTokenizer stok;FastScanner(InputStream is) {br = new BufferedReader(new InputStreamReader(is));}
        String next() throws IOException {while (stok == null || !stok.hasMoreTokens()) {String s = br.readLine();if (s == null) {return null;}
                stok = new StringTokenizer(s);}return stok.nextToken();}
        int ni() throws IOException {    return Integer.parseInt(next());}
        long nl() throws IOException {return Long.parseLong(next());}
        double nd() throws IOException {return Double.parseDouble(next());}
        char nc() throws IOException {return (char) (br.read());}
        String ns() throws IOException {return br.readLine();}
        int[] nia(int n) throws IOException{int a[] = new int[n];for (int i = 0; i < n; i++)a[i] = ni();return a;}
        long[] nla(int n) throws IOException {
            long a[] = new long[n];for (int i = 0; i < n; i++)a[i] = nl();return a;}
        double[] nda(int n)throws IOException {double a[] = new double[n];for (int i = 0; i < n; i++)        a[i] = nd();    return a;}
        int [][] imat(int n,int m) throws IOException
        {   int mat[][]=new int[n][m];for(int i=0;i<n;i++){   for(int j=0;j<m;j++)mat[i][j]=ni();}return mat;}
        
    }
        
    static long mod=Long.MAX_VALUE;
	public static void main (String[] args) throws java.lang.Exception
	{   int i,j;
	    HashMap<Integer,Integer> hm=new HashMap<Integer,Integer>();
		/*  if(hm.containsKey(z))
		        hm.put(z,hm.get(z)+1);
		    else
		        hm.put(z,1);
		 */       
        ArrayList<Long> arr=new ArrayList<>();
        HashSet<Integer> set=new HashSet<Integer>();
        PriorityQueue<Integer> pq=new PriorityQueue<Integer>();
        
        long r=in.nl();
        long x1=in.nl();
        long y1=in.nl();
        long x2=in.nl();
        long y2=in.nl();
        double dis=0;
        dis=Math.sqrt(Math.pow(x1-x2,2)+Math.pow(y1-y2,2));
        long ans=0;
        //out.println("dis="+dis);
        double z=2.0*r;
        if(dis==0.0)
            ans=0;
        else if(dis%z==0)
            ans=(long)(dis/z);
        else
            ans=(long)(dis/z)+1;
        //else if(dis>0 && dis<=)
        
        out.println(ans);
        out.close();
	}
	
	
	
	
	
	static long gcd(long a,long b)
	{   if(b==0)
	        return a;
	    return gcd(b,a%b);    
	}
	static long exponent(long a,long n)
	{   long ans=1;
	    while(n!=0)
	    {   if(n%2==1)
	            ans=(ans*a)%mod;
	       a=(a*a)%mod;
	       n=n>>1;
	    }
	    return ans;
	}
	static int binarySearch(int a[], int item, int low, int high) 
    {   if (high <= low) 
            return (item > a[low])?  (low + 1): low; 
        int mid = (low + high)/2; 
        if(item == a[mid]) 
            return mid+1; 
        if(item > a[mid]) 
            return binarySearch(a, item, mid+1, high); 
        return binarySearch(a, item, low, mid-1); 
    } 
   static void merge(int arr[], int l, int m, int r) 
    {   int n1 = m - l + 1; int n2 = r - m; int L[] = new int [n1]; int R[] = new int [n2]; 
        
        for (int i=0; i<n1; ++i) L[i] = arr[l + i]; for (int j=0; j<n2; ++j) R[j] = arr[m + 1+ j]; int i = 0, j = 0; int k = l; 
        while (i < n1 && j < n2) {   if (L[i] <= R[j]) {   arr[k] = L[i]; i++; } else{   arr[k] = R[j]; j++; } k++; } while (i < n1){   arr[k] = L[i]; i++; k++; } while (j < n2) { arr[k] = R[j];   j++;     k++; } 
    } 
    static void Sort(int arr[], int l, int r) 
    {    if (l < r) {   int m = (l+r)/2; Sort(arr, l, m); Sort(arr , m+1, r); merge(arr, l, m, r); } } 
    
    static void sort(int a[])
    {Sort(a,0,a.length-1);}

}