#include <iostream>
#include <fstream>

using namespace std;
ifstream f("ciur.in");
ofstream g("ciur.out");
int i,j,m,n, sol;
char v[2000005];
int main()
{
    f>>n;
    m=0;
    /*for(i=2;i*i<=n;i++)
    {
        if(v[i]==0)
        {
            for(j=i*i;j<=n;j=j+i)
            v[j]=1;
        }

    }
    for(i=2;i<=n;i++)
        if(v[i]==0)
            m++;*/
    sol = 1;
    for(i = 3; i * i <= n; i += 2)
        if(v[i] == 0)
            for(j = i * i; j <= n; j += i)
                v[i] = 1;
    for(i = 3; i <= n; i += 2)
        sol += (v[i] == 0);
    g<<sol;
    return 0;
}