#include<stdio.h>
#include<math.h>
char v[2000007];
long n;
void ciur(long n)
{
    long i,j;
    v[0]=v[1]='1';
    for (i=4;i<=n;i=i+2)
        v[i]='1';
    for (i=3;i<=sqrt(n);i=i+2)
        if (v[i]==0)
            for (j=i*2;j<=n;j=j+i)
                v[j]='1';
}
int main()
{
    freopen("ciur.in","r",stdin);
    freopen("ciur.out","w",stdout);
    scanf("%ld",&n);
    long nr,i;
    ciur(n);
    for (i=1;i<=n;i++)
        if (v[i]==0)
            nr++;
    printf("%ld",nr);
}