#include<stdio.h>

#define MAXN 2000001

bool ciur[MAXN];

int main () {

    FILE *f,*g;
    f=fopen("ciur.in","r");
    g=fopen("ciur.out","w");

    int n, i, j,nr;

    fscanf(f,"%d",&n);

    for( int i = 2; i*i <= n; ++i)
        for(j=i; j*i <= n; ++j)
        {
            ciur[i*j]=1;
        }
    ciur[0]=ciur[1]=1;
    nr=0;
    for(i=0; i<=n; ++i)
        if(ciur[i]==0)
            nr++;

    fprintf(g,"%d\n",nr);

    fclose(f);
    fclose(g);

    return 0;
}