Imagine you have an infinite 2D plane with Cartesian coordinate system. Some of the integral points are blocked, and others are not. Two integral points A and B on the plane are 4-connected if and only if:

  * the Euclidean distance between A and B is one unit and neither A nor B is blocked; 
  * or there is some integral point C, such that A is 4-connected with C, and C is 4-connected with B. 



Let's assume that the plane doesn't contain blocked points. Consider all the integral points of the plane whose Euclidean distance from the origin is no more than n, we'll name these points special. Chubby Yang wants to get the following property: no special point is 4-connected to some non-special point. To get the property she can pick some integral points of the plane and make them blocked. What is the minimum number of points she needs to pick?

Input

The first line contains an integer n (0 ≤ n ≤ 4·107).

Output

Print a single integer — the minimum number of points that should be blocked.

Examples

Input

1


Output

4


Input

2


Output

8


Input

3


Output

16
/*Talent is something you make bloom , instinct is something you polish*/
import java.io.*;
import java.math.*;
import java.util.*;
public class Main
{
    static long mod=((long)1e9)+7;//toString
    public static int gcd(int a,int b){if(b==0)return a;else return gcd(b,a%b);}
    public static long pow_mod(long x,long y){long res=1;x=x%mod;while(y > 0){if((y & 1)==1)res=(res * x)%mod;y=y>>1;x =(x * x)%mod;}return res;}
    public static int lower_bound(int[]arr,int val){int lo=0;int hi=arr.length-1;while(lo<hi){int mid=lo+((hi-lo+1)/2);if(arr[mid]==val){return mid;}else if(arr[mid]>val){hi=mid-1;}else lo=mid;}if(arr[lo]<=val)return lo;else return -1;}
    public static int upper_bound(int[]arr,int val){int lo=0;int hi=arr.length-1;while(lo<hi){int mid=lo+((hi-lo)/2);if(arr[mid]==val){return mid;}else if(arr[mid]>val){hi=mid;;}else lo=mid+1;}if(arr[lo]>=val)return lo;else return -1;}
    
    public static void main (String[] args) throws java.lang.Exception
    {
        Reader sn = new Reader();
        Print p = new Print();
        int n = sn.nextInt();
        if(n == 0)
        p.printLine("1");
        if(n == 1)
        p.printLine("4");
        if(n == 2)
        p.printLine("8");
        if(n >= 3)
        p.printLine(Integer.toString(4 * (int)(Math.sqrt(2) * n)));
        p.close();
    }
}
class Pair implements Comparable<Pair> {
		int val;
		int in;
		Pair(int a, int b){
			val=a;
	        in=b;
		}
		@Override
		public int compareTo(Pair o) {
			if(val==o.val)
			return Integer.compare(in,o.in);
			else
			return Integer.compare(val,o.val);
		}}
class Reader
    {
        final private int BUFFER_SIZE = 1 << 16;
        private DataInputStream din;
        private byte[] buffer;
        private int bufferPointer, bytesRead;
        public boolean isSpaceChar(int c) { return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1; }
        public Reader()
        {
            din = new DataInputStream(System.in);
            buffer = new byte[BUFFER_SIZE];
            bufferPointer = bytesRead = 0;
        }
 
        public Reader(String file_name) throws IOException
        {
            din = new DataInputStream(new FileInputStream(file_name));
            buffer = new byte[BUFFER_SIZE];
            bufferPointer = bytesRead = 0;
        }
 
        public String readLine() throws IOException
        {
            byte[] buf = new byte[64]; // line length
            int cnt = 0, c;
            while ((c = read()) != -1)
            {
                if (c == '\n')
                    break;
                buf[cnt++] = (byte) c;
            }
            return new String(buf, 0, cnt);
        }
        
        public String readWord()throws IOException
        {
		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 int nextInt() throws IOException
        {
            int ret = 0;
            byte c = read();
            while (c <= ' ')
                c = read();
            boolean neg = (c == '-');
            if (neg)
                c = read();
            do
            {
                ret = ret * 10 + c - '0';
            }  while ((c = read()) >= '0' && c <= '9');
 
            if (neg)
                return -ret;
            return ret;
        }
 
        public long nextLong() throws IOException
        {
            long ret = 0;
            byte c = read();
            while (c <= ' ')
                c = read();
            boolean neg = (c == '-');
            if (neg)
                c = read();
            do {
                ret = ret * 10 + c - '0';
            }
            while ((c = read()) >= '0' && c <= '9');
            if (neg)
                return -ret;
            return ret;
        }
 
        public double nextDouble() throws IOException
        {
            double ret = 0, div = 1;
            byte c = read();
            while (c <= ' ')
                c = read();
            boolean neg = (c == '-');
            if (neg)
                c = read();
 
            do {
                ret = ret * 10 + c - '0';
            }
            while ((c = read()) >= '0' && c <= '9');
 
            if (c == '.')
            {
                while ((c = read()) >= '0' && c <= '9')
                {
                    ret += (c - '0') / (div *= 10);
                }
            }
 
            if (neg)
                return -ret;
            return ret;
        }
 
        private void fillBuffer() throws IOException
        {
            bytesRead = din.read(buffer, bufferPointer = 0, BUFFER_SIZE);
            if (bytesRead == -1)
                buffer[0] = -1;
        }
 
        private byte read() throws IOException
        {
            if (bufferPointer == bytesRead)
                fillBuffer();
            return buffer[bufferPointer++];
        }
 
        public void close() throws IOException
        {
            if (din == null)
                return;
            din.close();
        }
    }
class Print
{
    private final BufferedWriter bw;
    public Print()
    {
        bw=new BufferedWriter(new OutputStreamWriter(System.out));
    }
    public void print(String str)throws IOException
    {
        bw.append(str);
    }
    public void printLine(String str)throws IOException
    {
        print(str);
        bw.append("\n");
    }
    public void close()throws IOException
    {
        bw.close();
    }}