#include <stdio.h>

int main(){
    FILE *fin,*fout;
    int n,i,ct,j;
    char v[2000000];

    fin=fopen("ciur.in","r");
    fout=fopen("ciur.out","w");
    fscanf(fin,"%d",&n);
    ct=0;
    for(i=3;i<n;i=i+2){
        v[i]=1;
    }
    if(n>=2){
        ct=1;
    }
    for(i=3;i<=n;i=i+2){
        for(j=3;j<i;j=j+2){
            if(i%j==0){
                v[i]=0;
            }
        }
        if(v[i]==1){
            ct++;
        }
    }
    fprintf(fout,"%d",ct);
    fclose(fin);
    fclose(fout);
    return 0;
}