#include <bits/stdc++.h>

using namespace std;

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

int a[2000100],n;

int main()
{
    int i,j,cnt;
    fin>>n;
    cnt=n+1;
    a[0]=1;
    a[1]=1;
    cnt-=2;
    for(i=4;i<=n;i+=2)
        {
            a[i]=1;
            cnt--;
        }
    for(i=3;i*i<=n;i+=2)
        if(a[i]==0)
            for(j=i*i;j<=n;j+=2*i)
            {
                a[j]=1;
                cnt--;
            }
    fout<<cnt;
    return 0;
}