#include <stdio.h>
#include <stdlib.h>
char ciur[2000000];
int main()
{
    FILE *fin, *fout;
    int ras=0,n,j,i;

    fin=fopen("ciur.in" , "r" );
    fout=fopen("ciur.out" , "w" );
    fscanf(fin, "%d" , &n);
    ciur[0]=ciur[1]=1;
    for(i=2;i*i<=n;i++)
        if(!ciur[i])
            for(j=i*i;j<=n;j=j+i)
                ciur[j]=1;
    printf("%d" , ciur[5]);
    for(i=2;i<=n;i++){
        if(ciur[i]==0)
            ras++;
    }
    fprintf(fout, "%d" , ras);
    fclose(fin);
    fclose(fout);
    return 0;
}