#include <stdio.h>
#include <stdlib.h>

char v[2000001];
int main()
{
    freopen("ciur.in","r",stdin);
    freopen("ciur.out","w",stdout);
    long n,k=1,j,i;
    scanf("%ld",&n);
    for(i=3;i<=n;i=i+2)
    {
        if(v[i]==0)
        {

            j=1;
            k++;
            while(i*j<=n)
            {
                v[i*j]=1;
                j++;
            }
        }
    }


    printf("%d",k);

    return 0;
}