#include <stdio.h>
char  v[2000008];
int main(){
FILE *in,*out;
in=fopen("ciur.in","r");
out=fopen("ciur.out","w");
int n;

int prime=0;
fscanf(in,"%d",&n);
int i,j;
for(i=2;i<=n;i++) {
    for(j=i+i;j<=n;j+=i) if(!v[j])
    { v[j]=1; prime++; }


}
prime=n-prime;
//for(i=2;i<=n;i++)  if(!v[i]) prime++;
fprintf(out,"%d",prime-1);
fclose(in);
fclose(out);
}