import java.io.IOException; import java.io.InputStream; import java.io.PrintWriter; import java.util.Arrays; import java.util.InputMismatchException; import java.util.NoSuchElementException; public class Main { static PrintWriter out; static InputReader ir; static void solve() { boolean[] p = new boolean[500001]; Arrays.fill(p, true); p[0] = p[1] = false; for (int i = 2; i <= Math.sqrt(500000); i++) { if (p[i]) { for (int j = i * 2; j <= 500000; j += i) { p[j] = false; } } } int n = ir.nextInt(); if (n == 1) { out.println(0); return; } int res = 0; for (int i = 3; i <= Math.sqrt(500000); i++) { if (p[i] && p[i * i - 2]) { if (n >= i * i - 2) res += 2; } } res++; out.println(res); } public static void main(String[] args) { ir = new InputReader(System.in); out = new PrintWriter(System.out); solve(); out.flush(); } static class InputReader { private InputStream in; private byte[] buffer = new byte[1024]; private int curbuf; private int lenbuf; public InputReader(InputStream in) { this.in = in; this.curbuf = this.lenbuf = 0; } public boolean hasNextByte() { if (curbuf >= lenbuf) { curbuf = 0; try { lenbuf = in.read(buffer); } catch (IOException e) { throw new InputMismatchException(); } if (lenbuf <= 0) return false; } return true; } private int readByte() { if (hasNextByte()) return buffer[curbuf++]; else return -1; } private boolean isSpaceChar(int c) { return !(c >= 33 && c <= 126); } private void skip() { while (hasNextByte() && isSpaceChar(buffer[curbuf])) curbuf++; } public boolean hasNext() { skip(); return hasNextByte(); } public String next() { if (!hasNext()) throw new NoSuchElementException(); StringBuilder sb = new StringBuilder(); int b = readByte(); while (!isSpaceChar(b)) { sb.appendCodePoint(b); b = readByte(); } return sb.toString(); } public int nextInt() { if (!hasNext()) throw new NoSuchElementException(); int c = readByte(); while (isSpaceChar(c)) c = readByte(); boolean minus = false; if (c == '-') { minus = true; c = readByte(); } int res = 0; do { if (c < '0' || c > '9') throw new InputMismatchException(); res = res * 10 + c - '0'; c = readByte(); } while (!isSpaceChar(c)); return (minus) ? -res : res; } public long nextLong() { if (!hasNext()) throw new NoSuchElementException(); int c = readByte(); while (isSpaceChar(c)) c = readByte(); boolean minus = false; if (c == '-') { minus = true; c = readByte(); } long res = 0; do { if (c < '0' || c > '9') throw new InputMismatchException(); res = res * 10 + c - '0'; c = readByte(); } while (!isSpaceChar(c)); return (minus) ? -res : res; } public double nextDouble() { return Double.parseDouble(next()); } public int[] nextIntArray(int n) { int[] a = new int[n]; for (int i = 0; i < n; i++) a[i] = nextInt(); return a; } public long[] nextLongArray(int n) { long[] a = new long[n]; for (int i = 0; i < n; i++) a[i] = nextLong(); return a; } public char[][] nextCharMap(int n, int m) { char[][] map = new char[n][m]; for (int i = 0; i < n; i++) map[i] = next().toCharArray(); return map; } } static void tr(Object... o) { out.println(Arrays.deepToString(o)); } }