#include <cstdio>
#define NMAX 2000000

FILE *f=fopen("ciur.in","r");
FILE *g=fopen("ciur.out","w");
int v[NMAX];
void ciur(int n)
{
    int i,j;
    for(i=2; i<=n; i++)
        if(v[i]==0)
            for(j=2; j*i<=n; j++)
                v[j*i]=1;
    v[1]=1;

}
void af(int n) // AFISARE VALORI CIUR
{
    int i;
    for(i=1;i<=n;i++)
        fprintf(g,"%d %c", v[i] ,' ');
}

int main()
{
    int n,i,k=0;
    fscanf(f,"%d",&n);
    ciur(n);

    for(i=1;i<=n;i++)
        if(v[i]==0)
            k++;
    fprintf(g,"%d",k);
    return 0;
}