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

int v[10000001];
int main()
{
    freopen("ciur.in","r",stdin);
    freopen("ciur.out","w",stdout);
    int n,k=0,j,i;
    scanf("%d",&n);
    for(i=2;i<=n;i++)
    {
        if(v[i]==0)
        {
            j=1;
            k++;
            while(i*j<=n)
            {
                v[i*j]=1;
                j++;
            }
        }
    }


    printf("%d ",k);

    return 0;
}