#include<fstream.h>
#define N 2000001
int main()
{long n,t,j,k,a[N]={0};
ifstream f("ciur.in");
ofstream g("ciur.out");
f>>n;
k=n-1;
for(j=2;j*j<=n;j++)
if(a[j]==0)
     for(t=2;t*j<=n;t++)
     if(a[t*j]==0)
          a[t*j]=1,k--;
g<<k;
return 0;}