#include <iostream>
#include <fstream>
#include <math.h>

using namespace std;
ifstream in("ciur.in");
ofstream out("ciur.out");
int n,x[2000002];
int main()
{ in>>n;int i,j,k=0;
double radb;
    radb=sqrt((double)n);
    for( i=2;i<=radb;i++)
            for(j=i*i;j<=n;j=j+i)
                {if(x[j]==0)k++;x[j]=1;}
    out<<n-k-1;
    return 0;
}