#include <bits/stdc++.h>

char ciur[2000001];

int main()
{
    int n,i,d,s=0;
    FILE*fi,*fo;
    fi=fopen("ciur.in","r");
    fo=fopen("ciur.out","w");
    fscanf(fi,"%d",&n);
    for(i=2;i*i<=n;i++){
        for(d=i*i;d<=n;d+=i){
            s+=1-ciur[d];
            ciur[d]=1;
        }
    }
    fprintf(fo,"%d",n-s-1);
    fclose(fi);
    fclose(fo);
    return 0;
}