#include <iostream>
#include <fstream>
using namespace std;
int main(){
    int i,j,n,s=0,ss,ii;
    ifstream f("fractii.in");
    ofstream g("fractii.out");
    f>>n;
    for(i=2;i<=n;i++){
        ii=i;
        ss=i;
        for(j=2;j<=ii;j++)if(ii%j==0){
            while(ii%j==0)ii=ii/j;
            ss=(ss*(j-1))/j;
        }
        s+=ss;
    }
    g<<s*2+1;
    return 0;
}