import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.StringTokenizer;
import java.util.TreeMap;
import java.io.IOException;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.InputStream;

public class c278b {
	
	static class TaskA
    {
        public void solve(int testNumber, InputReader in, PrintWriter out) 
        {
        	int r=in.nextInt();
        	int x1=in.nextInt();
        	int y1=in.nextInt();
        	int x2=in.nextInt();
        	int y2=in.nextInt();
        	double dis=Math.sqrt(Math.pow(x1-x2,2)+Math.pow(y1-y2,2));
        	if(dis%(2*r)!=0)
        	{
        		out.print((int)dis/(2*r)+1);
        	}
        	else
        	{
        		out.print((int)dis/(2*r));
        	}
           
        }
    }
       
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        TaskA solver = new TaskA();
        solver.solve(1, in, out);
        out.close();
    }
    
  
    
    /* java.util.Arrays.sort(array_name,new java.util.Comparator<int[]>(){
    public int compare(int[] a, int[] b) {
        return Integer.compare(a[0], b[0]);
    }}); */
    
    static void radixSort(int[] xs){
		int[] cnt = new int[(1<<16)+1];
		int[] ys = new int[xs.length];	
		for(int j = 0; j <= 16; j += 16) 
		{	Arrays.fill(cnt, 0);
			for(int x : xs) { cnt[(x>>j&0xFFFF)+1]++; }
			for(int i = 1; i < cnt.length; i++) { cnt[i] += cnt[i-1]; }
			for(int x : xs) { ys[cnt[x>>j&0xFFFF]++] = x; }
			{ final int[] t = xs; xs = ys; ys = t; }   }
		if(xs[0] < 0 || xs[xs.length - 1] >= 0) 
			return;
		int i, j, c;
		for(i = xs.length - 1, c = 0; xs[i] < 0; i--, c++) { ys[c] = xs[i]; }
		for(j = xs.length - 1; i >= 0; i--, j--) { xs[j] = xs[i]; }
		for(i = c - 1; i >= 0; i--) { xs[i] = ys[c-1-i]; }
	}
   
    static long min(long x,long y){return x<y?x:y;}
    static long min(long x,long y,long z){return x<y?(x<z?x:z):(y<z?y:z);}
    static long min(long n1,long n2,long n3,long n4){
    	return n1<n2?(n1<n3?(n1<n4?n1:n4):(n3<n4?n3:n4)):(n2<n3?(n2<n4?n2:n4):(n3<n4?n3:n4));}
    static long max(long x,long y){return x>y?x:y;}
    static long max(long x,long y,long z){return x>y?(x>z?x:z):(y>z?y:z);}
    static long max(long n1,long n2,long n3,long n4){
    	return n1>n2?(n1>n3?(n1>n4?n1:n4):(n3>n4?n3:n4)):(n2>n3?(n2>n4?n2:n4):(n3>n4?n3:n4));}
    static int min(int x,int y){return x<y?x:y;}
    static int min(int x,int y,int z){return x<y?(x<z?x:z):(y<z?y:z);}
    static long min(int n1,int n2,int n3,int n4){
    	return n1<n2?(n1<n3?(n1<n4?n1:n4):(n3<n4?n3:n4)):(n2<n3?(n2<n4?n2:n4):(n3<n4?n3:n4));}
    static int max(int x,int y){return x>y?x:y;}
    static int max(int x,int y,int z){return x>y?(x>z?x:z):(y>z?y:z);}
    static long max(int n1,int n2,int n3,int n4){
    	return n1>n2?(n1>n3?(n1>n4?n1:n4):(n3>n4?n3:n4)):(n2>n3?(n2>n4?n2:n4):(n3>n4?n3:n4));}
    
    static long sumarr(int arr[],int n1,int n2){
    	long sum=0; for(int i=n1-1;i<n2;i++) sum=sum+arr[i];  return sum; }
    
    
     
//**************************************Reader Class*********************************************//
    
    static class InputReader {
        public BufferedReader reader;
        public StringTokenizer tokenizer;

        public InputReader(InputStream stream) {
            reader = new BufferedReader(new InputStreamReader(stream), 32768);
            tokenizer = null;
        }

        public String next() {
            while (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    tokenizer = new StringTokenizer(reader.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken();
        }
        
        public String nextLine() {
			String fullLine=null;
			while (tokenizer == null || !tokenizer.hasMoreTokens()) {
				try {
					fullLine=reader.readLine();
				} catch (IOException e) {
					throw new RuntimeException(e);
				}
				return fullLine;
			}
			return fullLine;
		}

        public int nextInt() {
            return Integer.parseInt(next());
        }
        
        public long nextLong() {
        	return Long.parseLong(next());
        }
        
        public double nextDouble() {
        	return Double.parseDouble(next());
        }

    }
}