#include <cstdio>

using namespace std;
int i, j, nr, n;
char v[125007];
int main()
{
    freopen("ciur.in", "r", stdin);
    freopen("ciur.out", "w", stdout);
    scanf("%d", &n);
    nr=1;
    for(i=1;((i*i) << 1)+(i << 1)<=n;i++)
        if((v[i>>3]&(1<<(i&7)))==0)
        {
            for(j=((i*i)<<1)+(i<<1);(j<<1)+1<=n;j+=(i<<1)+1)
                v[j>>3] |= (1<<(i&7));
        }
    for(i=1;2*i+1<=n;i++)
        if((v[i>>3]&(1<<(i&7)))==0)
            nr++;
    printf("%d", nr);
    return 0;
}