#include <cstdio>
#define Nmax 2000005

using namespace std;

bool ciur[Nmax];

inline void Ciur()
{
    int i,j;
    for(i=3;i<=1415;i+=2)
        if(!ciur[i])
            for(j=i*i;j<=2000000;j+=2*i)
                ciur[j]=true;
}

int main()
{
    int sol=1,i,N;
    freopen ("ciur.in","r",stdin);
    freopen ("ciur.out","w",stdout);
    Ciur();
    scanf("%d", &N);
    for(i=3;i<=N;i+=2)
        if(!ciur[i])
            ++sol;
    printf("%d\n", sol);
    return 0;
}