#include<bits/stdc++.h>

using namespace std;

ifstream fin("ciur.in");
ofstream fout("ciur.out");

bitset<10000001> a;
int main()
{
    long long n,i,j,r=0;
    fin>>n;
    a[0]=1;
    a[1]=1;
    a[2]=0;
    for(i=4;i<=n;i+=2)
        a[i]=1;
    for(i=3;i<=n;i+=2)
        if(a[i]==0)
            for(j=i*i;j<=n;j+=(i*2))
                a[j]=1;
    for(i=1;i<=n;i++)
        if(a[i]==0)
            r++;
    fout<<r;
    return 0;
}