#include <fstream>

using namespace std;
ifstream in ("ciur.in");
ofstream out ("ciur.out");
bool ciur[10000];
int main()
{
long long i,j,n,cnt=0;
for (i=4; i<=10000; i=i+2)
{
    ciur[i]=1;
}
for (i=3; i<=10000; i+=2)
{
    for (j=2; i*j<=10000; j++)
        ciur[i*j]=1;
}
in>>n;
for (i=1; i<=n; i++)
{
    if (ciur[i]==0)
        cnt++;
}
out<<cnt-1;
        return 0;
}