#include <cstdio>
#define MAX 2000002

unsigned char p[MAX/8];

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(){
    int n;
    freopen("ciur.in","r",stdin);
    freopen("ciur.out","w",stdout);

    ciur();
        scanf("%d",&n);

    int nr = 0;
    for(int i=2;i<=n;i++)
    if((p[i/8]&1<<i%8) == 0)nr++;
        printf("%d\n",nr);

    return 0;
}