#include <bits/stdc++.h>

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