include <bits/stdc++.h>
 
using namespace std;

static const long MAX = 1000000L;
 
int main() {
    vector<long> prime;
    bool isPrime;
    long n;
 
    long i, len = sqrt(MAX) + 1;
    long j, lenJ;
    long k;
     
    prime.push_back(2);

    for (i = 3; i <= len; i += 2) {
        isPrime = true;
        lenJ = prime.size();
        k = sqrt(i) + 1;
        for (j = 0; j < lenJ; j++) {
            if (k <= prime[j]) break;

            if (i % prime[j] == 0) {
                isPrime = false;

                break;
            }

        if (isPrime) prime.push_back(i);
    }

    lenJ = prime.size();
     
    while (cin >> n) {
        counter = 1;

        if (n < 2) counter = 0;
         
        for (i = 3; i <= n; i += 2) {
            isPrime = true;

            k = sqrt(i) + 1;
            for (j = 0; j < lenJ; j++) {
                if (k <= prime[j]) break;

                if (i % prime[j] == 0) {
                    isPrime = false;

                    break;
                }
            }

            if (isPrime) counter++;
        }
         
        cout << counter << endl;
    }
 
    return 0;
}