#include <bits/stdc++.h>
using namespace std;
ifstream fin("ciur.in");
ofstream fout("ciur.out");
int n,i,ciur[2000010],j,p;
int main()
{
    fin>>n;
    ciur[0]=ciur[1]=1;
    for(i=4;i*i<=2000000;i=i+2)
        ciur[i]=1;
    for(i=3;i*i<=2000000;i=i+2)
        for(j=2;j*i<=2000000;j++)
            ciur[i*j]=1;
    for(i=1;i<=n;i++)
        if(!ciur[i])
            p++;
    fout<<p;
    return 0;
}