#include <bits/stdc++.h>
#define MAX 5000005
using namespace std;

ifstream in("ciur.in");
ofstream out("ciur.out");

int n, cnt;
bitset < MAX > c;

int main(){
    in>>n;
    cnt = 1;
    for(int i = 3; i * i <= n; i += 2)
        for(int j = i * i; j <= n; j += 2 * i)
            c[j] = 1;
    for(int i = 3; i <= n; i += 2)
        if(!c[i])
            cnt++;
    out<<cnt;
}