#include <stdio.h>
#define nmax 2000000
using namespace std;
int nrc,n;
char prim[2000005];

int main(){

    freopen("ciur.in","r",stdin);
    freopen("ciur.out","w",stdout);
    scanf("%d",&n);
    for(int i=2;i<=n;++i)
            prim[i]=1;
    for(int i=2;i<=n;i++)
    if(prim[i]==1){
            nrc++;
        for(int k=i+i;k<=n;k+=i)
        if(prim[k]==1){
        prim[k]=0;
    }
    }
        //for(int i=2;i<=n;++i)
        printf("%d ",nrc);
    return 0;
}