import std.conv, std.functional, std.range, std.stdio, std.string;
import std.algorithm, std.array, std.bigint, std.complex, std.container, std.math, std.numeric, std.regex, std.typecons;
import core.bitop;

class EOFException : Throwable { this() { super("EOF"); } }
string[] tokens;
string readToken() { for (; tokens.empty; ) { if (stdin.eof) { throw new EOFException; } tokens = readln.split; } auto token = tokens.front; tokens.popFront; return token; }
int readInt() { return readToken.to!int; }
long readLong() { return readToken.to!long; }
real readReal() { return readToken.to!real; }

bool chmin(T)(ref T t, in T f) { if (t > f) { t = f; return true; } else { return false; } }
bool chmax(T)(ref T t, in T f) { if (t < f) { t = f; return true; } else { return false; } }

int binarySearch(alias pred, T)(in T[] as) { int lo = -1, hi = cast(int)(as.length); for (; lo + 1 < hi; ) { const mid = (lo + hi) >> 1; (unaryFun!pred(as[mid]) ? hi : lo) = mid; } return hi; }
int lowerBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a >= val)); }
int upperBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a > val)); }


enum LIM = 5 * 10^^5 + 10;

void main() {
  auto isnp = new bool[LIM];
  int[] primes;
  foreach (p; 2 .. LIM) {
    if (!isnp[p]) {
      primes ~= p;
      for (int n = 2 * p; n < LIM; n += p) {
        isnp[n] = true;
      }
    }
  }
  stderr.writeln("|primes| = ", primes.length);
  
  try {
    for (; ; ) {
      const N = readInt();
      int ans;
      foreach (r; primes) {
        if (r * r > N) {
          break;
        }
        foreach (p; primes) {
          const q = r * r - p;
          if (q < 2) {
            break;
          }
          if (!isnp[q]) {
            ++ans;
          }
        }
      }
      writeln(ans);
    }
  } catch (EOFException e) {
  }
}