#include <bits/stdc++.h>

using namespace std;
ifstream f("ciur.in");
ofstream g("ciur.out");
bitset<1000010> b;
int n,m,i,k,sol,j;
int main()
{
    f>>n;
    if(n%2==0)
        n--;
    m=(n-1)/2;
    for(i=1,k=3;k*k<=n;i++,k+=2)
        if(!b[i])
            for(j=2*i*(i+1);j<=m;j+=k)
                b[j]=1;
    g<<m-b.count()+1;
    return 0;
}