#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++)
    {
        if(ciur[i]==0)
        {
            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;
}