#include <bits/stdc++.h>

using namespace std;
ifstream f("ciur.in");
ofstream g("ciur.out");
const int N = 2000010;
int n,i,j,cnt;
bitset<N> p;
int main() {
    f >> n;
    p.set();
    p[0]=p[1]=0;
    for(i=3; i*i<=n; i+=2)
        if(p[i])
            for(j=i*i; j<=n; j+=2*i)
                p[j]=0;
    cnt=p.count()-N+n+2-n/2;
    g<<cnt;
}