#include <stdio.h>
#include <stdlib.h>
#define MAXINT 1000001
int v[MAXINT], i, n,j,ans;
int main()
{
    scanf("%d", &n);
    for (i = 3; i <= sqrt(n); i += 2)
        for (j = i * 3 ; j <= n; j += i<<1)
            v[j] = 1;

    for (i = 3; i <= n; i += 2)
        if (v[i] == 0)
            ans++;

    if(n >= 2)  ans++;

    printf("%d\n",ans);
    return 0;
}