#include <bits/stdc++.h>
using namespace std;
ifstream in("ciur.in");
ofstream out("ciur.out");
int power(int x, unsigned int y, int p) {
    int res = 1;
    x = x % p;
    while (y > 0) {
        if (y & 1)
            res = (res*x) % p;
        y = y>>1;
        x = (x*x) % p;
    }
    return res;
}
bool miillerTest(int d, int n) {
    int a = 2 + rand() % (n - 4);
    int x = power(a, d, n);
    if (x == 1  || x == n-1)
        return true;
    while (d != n-1) {
        x = (x * x) % n;
        d *= 2;

        if (x == 1)      return false;
        if (x == n-1)    return true;
    }
    return false;
}
bool isPrime(int n, int k) {
    if (n <= 1 || n == 4)  return false;
    if (n <= 3) return true;
    int d = n - 1;
    while (d % 2 == 0)
        d /= 2;
    for (int i = 0; i < k; i++)
        if (miillerTest(d, n) == false)
            return false;
    return true;
}
int main() {
    int k=4;
    int c1=0,c;
    in>>c;
    for (int n = 2; n <= c; n++)
        if (isPrime(n, k))
            c1++;
    out<<c1;
    return 0;
}