# include <iostream># include <fstream># include <bitset>using namespace std; # define MAXN 2000003 ifstream f("ciur.in");ofstream g("ciur.out"); bitset<MAXN> prim; int main(){    int n, s = 0;    f >> n;     prim.set();    for (int i = 2; i <= n; i++) {        if (prim[i] == true) {            s++;            for (int j = i + i; j <= n; j += i) {                prim[j] = false;            }        }    }     g << s;     return 0;}