#include<stdio.h>
#include<string.h>
int n,cnt=0;
//char *Prime;//Prime[i]==1 => Prime[i] nu e prim
char Prime[2000001];

void pregateste()
{
FILE *pin=fopen("ciur.in","r");
fscanf(pin,"%d",&n);
//Prime=new char[n/16+1];
//memset(Prime,0,sizeof(Prime)*(n/16+1));
for(int i=0;i<=n;i++)
  Prime[i]=0;
fclose(pin);}

void rezolva()
{long long int i,j;
for(i=3;i<=n;i+=2)
  if(/*( Prime[i/16] & (1<<(i/2%8)))==0*/ Prime[i]==0)
    {
    cnt++;
    for(j=i*i;j<=n;j+=i*2)
      //Prime[j/16]|=(1<<(j/2%8));
      Prime[j]=1;
    }
}

void incheie()
{//delete []Prime;
FILE *pout=fopen("ciur.out","w");
fprintf(pout,"%d",cnt+1);
fclose(pout);}

int main()
{
pregateste();
rezolva();
incheie();
return 0;
}