#include <stdlib.h>
#include <math.h>
#include <stdio.h>
int main()
{
    int *a,n,l=1, i, j;
    freopen("ciur.in" , "rt", stdin);
    freopen("ciur.out", "wt", stdout);

    scanf("%d", &n);
    a = (int *) malloc((n+1)*sizeof(int));
    for(i=1;i<=n;++i)
        a[i] = 1;
    for(i=2;i<=sqrt(n);++i)
        if(a[i])
            for(j=1;j<=n/i;++j)
                a[i*j] = 0;
    for(i=1;i<=n;++i)
        if(a[i])
            l++;

    printf("%d", l);

    return 0;

}