import java.io.OutputStream; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.io.PrintWriter; import java.io.BufferedWriter; import java.io.Writer; import java.util.Set; import java.io.OutputStreamWriter; import java.util.InputMismatchException; import java.io.IOException; import java.util.TreeSet; import java.io.InputStream; import java.util.ArrayList; /** * Built using CHelper plug-in * Actual solution is at the top */ 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); No843 solver = new No843(); solver.solve(1, in, out); out.close(); } static class No843 { public void solve(int testNumber, InputReader in, OutputWriter out) { int n = in.readInt(); Set primes = new TreeSet<>(new Prime(n).getPrimes()); int ans = 0; for (int prime : primes) { if (prime * prime > n + 2) break; if (primes.contains(prime * prime - 2)) ans++; } out.printLine(n == 1 ? 0 : 2 * ans - 1); } } static class Prime { private int n; private boolean[] isPrime; private ArrayList primes; public Prime(int n) { this.n = n; isPrime = new boolean[n + 1]; primes = new ArrayList<>(); sieve(); } private void sieve() { for (int i = 2; i <= n; i++) { if (!isPrime[i]) { primes.add(i); for (long j = (long) i * i; j <= n; j += i) { isPrime[(int) j] = true; } } } } public ArrayList getPrimes() { return primes; } } static class InputReader { private InputStream stream; private byte[] buf = new byte[1024]; private int curChar; private int numChars; private InputReader.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 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 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; } public interface SpaceCharFilter { public boolean isSpaceChar(int ch); } } static 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 close() { writer.close(); } public void printLine(int i) { writer.println(i); } } }