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
import java.io.BufferedWriter;
import java.util.InputMismatchException;
import java.io.InputStream;
import java.util.NoSuchElementException;
import java.io.OutputStreamWriter;
import java.math.BigInteger;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.io.Writer;
import java.io.IOException;
import java.util.*;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 * @author Árysson Cavalcanti
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        OutputWriter out = new OutputWriter(outputStream);
        TaskE solver = new TaskE();
        solver.solve(1, in, out);
        out.close();
    }
}

class TaskE {
    public void solve(int testNumber, InputReader in, OutputWriter out) {
        int n=in.readInt(), ret=n, x=n;
        for (int y=1; y<=n; y++) {
            if (1L*x*x+1L*y*y>1L*n*n) x--;
            while (1L*x*x+1L*y*y>1L*n*n) {
                x--;
                ret++;
            }
        }
        ret=n==0?1:4*ret;
        out.printLine(ret);
    }
}

class InputReader {
        private boolean finished = false;

        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 peek() {
                if (numChars == -1)
                        return -1;
                if (curChar >= numChars) {
                        curChar = 0;
                        try {
                                numChars = stream.read(buf);
                        } catch (IOException e) {
                                return -1;
                        }
                        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 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 String readString() {
                int c = read();
                while (isSpaceChar(c))
                        c = read();
                StringBuilder res = new StringBuilder();
                do {
                        if (Character.isValidCodePoint(c))
                                res.appendCodePoint(c);
                        c = read();
                } while (!isSpaceChar(c));
                return res.toString();
        }

        public boolean isSpaceChar(int c) {
                if (filter != null)
                        return filter.isSpaceChar(c);
                return isWhitespace(c);
        }

        public static boolean isWhitespace(int c) {
                return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }

        private String readLine0() {
                StringBuilder buf = new StringBuilder();
                int c = read();
                while (c != '\n' && c != -1) {
                        if (c != '\r')
                                buf.appendCodePoint(c);
                        c = read();
                }
                return buf.toString();
        }

        public String readLine() {
                String s = readLine0();
                while (s.trim().length() == 0)
                        s = readLine0();
                return s;
        }
        
        String readLine(boolean ignoreEmptyLines) {
                if (ignoreEmptyLines)
                        return readLine();
                else
                        return readLine0();
        }

        public BigInteger readBigInteger() {
                try {
                        return new BigInteger(readString());
                } catch (NumberFormatException e) {
                        throw new InputMismatchException();
                }
        }

        public char readCharacter() {
                int c = read();
                while (isSpaceChar(c))
                        c = read();
                return (char) c;
        }
        
        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 boolean isExhausted() {
                int value;
                while (isSpaceChar(value = peek()) && value != -1)
                        read();
                return value == -1;
        }
        
        public String next() {
                return readString();
        }

        public SpaceCharFilter getFilter() {
                return filter;
        }

        public void setFilter(SpaceCharFilter filter) {
                this.filter = filter;
        }

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

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(char[] array) {
                writer.print(array);
        }

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

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

    public void print(long[] array) {
        for (int i = 0; i < array.length; i++) {
            if (i != 0)
                writer.print(' ');
            writer.print(array[i]);
        }
    }
    
        public void printLine(int[] array) {
        print(array);
        writer.println();
    }

    public void printLine(long[] array) {
        print(array);
        writer.println();
    }

        public void printLine() {
                writer.println();
        }

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

        public void print(char i) {
                writer.print(i);
        }

        public void printLine(char i) {
                writer.println(i);
        }
        
        public void printLine(char[] array) {
                writer.println(array);
        }

        public void printFormat(String format, Object...objects) {
                writer.printf(format, objects);
        }

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

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

        public void print(long i) {
                writer.print(i);
        }

        public void printLine(long i) {
                writer.println(i);
        }

        public void print(int i) {
                writer.print(i);
        }

        public void printLine(int i) {
                writer.println(i);
        }
}