#include <bits/stdc++.h>

using namespace std;
ifstream fin("ciur.in");
ofstream fout("ciur.out");
int n,c[2000005],co,j,i;
int main()
{fin>>n;
   c[1]=c[0]=1;
   for(int i=2;i*2<=n;i++)
    c[i*2]=1;
    for(int i=3;i*i<=n;i=i+2)
    if(c[i]==0)
    for(j=2;j*i<=n;j++)
    c[i*j]=1;
    for(i=1;i<=n;i++)
    co++;
   cout<<co;
}