#include <cstdio>

#define Max 2000002

int n,nr;
unsigned char p[Max>>3];

void ciur()
{
    int i=2;
    while(i<=1414)
    {
        while(p[i/8] & 1<<(i%8))i++;
        for(int j=i*i;j<Max;j+=i)p[j/8]|=1<<(j%8);
        i++;
    }
}

int main()
{
    freopen("ciur.in","r",stdin);
    freopen("ciur.out","w",stdout);
        scanf("%d",&n);
        ciur();
    for(int i=2;i<=n;i++)
    if(!(p[i/8] & 1<<(i%8)))nr++;//printf("%d ",i);

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